- Email: [email protected]
New technologies for an effective energy retrofit of hospitals
Applied Thermal Engineering 26 (2006) 161–169 www.elsevier.com/locate/apthermeng
New technologies for an effective energy retrofit of hospitals Giacomo Bizzarri a
a,*
, Gian Luca Morini
b
Dipartimento di Architettura, Universita` degli Studi di Ferrara, Via Quartieri, 8-44100 Ferrara, Italy b DIENCA, Universita` degli Studi di Bologna, Viale Risorgimento, 2-40136 Bologna, Italy Received 13 March 2005; accepted 26 May 2005 Available online 18 July 2005
Abstract Following the approval by the European Parliament of the directive on energy efficiency of public buildings, a great effort has been directed towards enhancing low-emission systems such as fuel cells (FC), photovoltaic systems (PVS) or solar thermal systems (STS), especially in all public facilities, such as hospitals, characterized by relevant energy requirements. This paper develops a theoretical analysis which focuses on the environmental benefits achievable through a shift from the conventional systems, normally operating in hospitals, to various hybrid plants. The model site is a hospital located near Ferrara (Italy). Several hybrid schemes were investigated and compared: PAFCs (phosporic acid fuel cells), STS and PVS. An energy analysis was developed for each option assuming, as a benchmark, the conventional systems operating today in the medical center. The results, presented with reference to the primary energy requirements and the pollutant emissions, demonstrate that in the case of existing systems being upgraded with these hybrid plants, overall emissions could be abated with a significant reduction in fossil energy consumption. Finally, an economic study, even taking external factors into account, is developed for all the retrofit scenarios in terms of annual return, simple payback period and IRR. 2005 Elsevier Ltd. All rights reserved. Keywords: Hybrid plants; Pollutant reductions; Primary energy savings; Fuel cells; Solar thermal systems; Photovoltaic systems
1. Introduction Theoretically, local governments have the potential to control, both directly and indirectly, a considerable amount of the greenhouse gases (GHGs) emitted, originated from the heating and cooling plants of public buildings (local government premises, hospitals, etc.) as well as from the supply of basic services such as transportation, water and waste management. Recently, the
Abbreviation: IRR, Internal rate of return. Corresponding author. Tel.: +39 0532 293653; fax: +39 0532 293627. E-mail addresses: [email protected] (G. Bizzarri), gianluca. [email protected] (G.L. Morini). *
1359-4311/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2005.05.015
European Parliament unanimously approved the proposed directive on energy efficiency of public buildings, whose objective is the control and reduction of energy consumption by 22% by the year 2010 [1]. One example of a simple, useful tool that local governments can harness in order to reduce GHG emissions in a meaningful way is to upgrade their buildingsÕ plants (municipalities, hospitals, decisional centers) with a shift away from the use of conventional fossil fuels toward more ecological, renewable energy sources. These technologies produce environmental benefits since non-renewable energy can be preserved and environmental pollution can be drastically reduced. In addition to this, the decentralization of the electricity production plants mitigates the grid distribution losses. In recent years, several studies have been developed in this field. Bizzarri and Morini [2] proved that
162
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
Nomenclature COPC compression chillers coefficient of performance COPAC absorption chillers coefficient of performance COP0AC absorption chillers (heat pump mode) coefficient of performance QC monthly cooling requirement (MW h) QE monthly electrical requirement except from electricity for compression chiller end use (MW h) E Q monthly electrical requirement (MW h) QH monthly heating requirement (MW h) Qp monthly primary fossil energy requirements (MW h) QpE monthly primary fossil energy requirements associated to thermo-electric power plant operation (MW h) QpFC fuel cells monthly primary fossil energy requirements (MW h) QpH monthly primary fossil energy requirements associated to boilers operation (MW h) Q0S monthly direct radiation at Lagosanto (lat. 44.5, lon. 12.1) (kW h/m2)
harnessing a fuel cell hybrid plant in a hospital can bring substantial primary energy savings, as well as a consistent drop in pollutant emissions. Van Schijndel [3] showed how the optimization of the primary energy consumption associated with the hospitalsÕ thermal plants operation can be compatible with the constraint of a positive economic profit. Ying and Hu [4] demonstrated that the use of solar energy is of great importance in reducing GHG emissions by analyzing a solar aided plant where solar heat is used to replace the extracted steam to heat the feedwater in the regenerative Rankine plant. Spiegel et al. [5], Krauter and Ruther [6], Gomez-Amo et al. [7] studied the potential of photovoltaic systems in terms of emission reduction. Recently, Ferguson and Ugursal [8] investigated the effect of varying fuel cells size on the performance of cogeneration systems. This paper is devoted to investigate the real opportunities in terms of primary energy and money savings and environmental benefits offered by the energy retrofit of a typical Italian hospital. The retrofit policies taken into consideration here consist in a shift from a conventional plant configuration (normally operating in the hospitals), to different hybrid schemes, as phosphoric acid fuel cells (PAFCs), solar thermal systems (STS) and photovoltaic systems (PVS). The hospital of Lagosanto, near Ferrara (Italy), has been chosen as a case study to test the efficacy of these retrofit strategies.
Q00S
monthly diffuse radiation at Lagosanto, (lat. 44.5, lon. 12.1) (kW h/m2)
Greek symbols gB gas-fired boilers thermal efficiency gcSTS monthly collectors efficiency, part of monthly direct radiation transferable into thermal energy by solar collectors gE,T public utility mean electrical efficiency geFC fuel cells electrical efficiency geSTS monthly solar thermal systems electrical efficiency ghFC fuel cell low enthalpy thermal recoveries efficiency ghSTS monthly solar thermal systems low enthalpy thermal recoveries efficiency gORC organic Rankine cycle efficiency gPV monthly photovoltaic systems electrical efficiency
2. Constraints of retrofit The energy requirements of the Lagosanto hospital have been determined according to the same procedures defined in previous studies [2,9,10] and are quoted in Table 1. Examination of Table 1 shows that the monthly electricity demand during summer grows significantly following a common pattern which distinguishes many north Italian hospitals [9]. This growth is due to the high utilization of compression chillers supporting the HVAC systems during the hot season. A peak cut policy, pursuing the optimization of the electrical requireTable 1 E Þ, heating (QH) and cooling (QC) Estimated monthly electrical ðQ demands of LagosantoÕs hospital Month
E [MW he] Q
QH [MW ht]
QC [MW ht]
January February March April May June July August September October November December
475.6 475.5 505.2 480.6 537.4 669.2 689.7 711.3 496.2 517.7 493.4 488.3
1714.5 1448.8 1269.8 893.9 460.3 232.4 134.3 138.9 232.6 636.8 1167.1 1600.2
– – – – 154.2 322.2 533.1 468.2 291.5 – – –
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
ments around the monthly values normally experienced during the colder months, could even produce financial benefits, given that the contracts with the electricity companies tend to be set to the peak of consumption. In this regard, solar technologies are well suited to peak cut purpose since these systems achieve their peak of production in accordance with peak demand during the hottest sunny days of the summer [10,11]. It has been proved that, for hybrid solar thermal power plants, the major fossil energy saving and reduction of greenhouse gases are obtained when the solar collectors provide an amount of electricity consistent with the summer growth of consumption [10]. Today, in the hospital of Lagosanto, heat and power requirements are provided by ‘‘conventional’’ systems. Electricity is imported from the grid whereas heating is completely supplied by gas-fired boilers. Compression chillers satisfy cooling needs. The retrofit scenarios presented in this article have been developed considering two main constraints. The first constraint is linked to plant size. A previous study [11] demonstrated that a plant sized in such a way that the monthly electricity ‘‘self-production’’ from the ‘‘non-conventional’’ part of the plant was equal to the gap that existed between the average monthly electricity requirement characteristic of summer months (from June to August) and that typical of other months brought considerable environmental benefits, but was shown not to be economically sustainable. With cost effectiveness being a basic target, it appeared interesting to look into both energy and economic analysis finally taking into account also externalities [12] and introducing a second case study consisting of a smaller plant. If the photovoltaic and solar thermal systems allow plants of varying sizes to be built, the PAFCs, chosen as the reference being the sole ones with sufficiently reliable data in the literature, are on the market in plants not smaller than 200 kW. This substantial difference has imposed as the main constraint that plant sizes had to be somehow linked to the market availability of PAFCs. It means system sizes could not be less than 200 kW. In particular, plant configurations were studied that would guarantee a production of electrical energy equivalent to that which would have been able to be achieved with an installation of up to 2 PAFCs. The following assumptions have also been taken into account. • Trigeneration is pursued: if low enthalpy heat recoveries are available they are used first to feed absorption chillers for cooling (only in summer), then to mitigate boiler operations (directly or indirectly, making absorption chillers work as heat pumps during the cold season).
163
• Absorption chillers are sized in such a way as to always be fed by the whole of the energy recoveries when these are available. • In the peak mode, the energy needs in deficit is supplied by the ‘‘conventional’’ systems: electricity is imported from the grid, heat and cold are generated respectively using gas-fired boilers and compression chillers. • Electricity from the grid is assumed to have been derived from a oil fired power station [13]. • The heat loss in the plant network is disregarded.
3. Plant configurations Four different plant configurations were investigated:
3.1. Basic configuration In this scheme, the following numerical values have been adopted: • public utility mean electrical efficiency gE,T = 39% [13,14], • gas-fired boilers seasonal thermal efficiency gB = 85%, • compression chiller COPC = 3.0. The monthly primary fossil energy requirements associated to the fulfillment of the whole of the hospitalÕs energy needs can be evaluated according to the following energy balance:
Qp ¼ QpE þ QpH ¼ ¼
1 gE;T
QE þ
QC Q þ H COPC gB
E QH Q þ . gE;T gB
ð1Þ
3.2. PAFC retrofit configuration Phosphoric acid fuel cells (PAFCs) hybrid plant shown in Fig. 1: the ‘‘non-conventional’’ part of the plant consists in PAFCs also integrated with an absorption cooling system. The heating is supplied partially by heat recoveries from the fuel cell and the remainder by gas-fired boilers. The fuel cells here investigated meet the characteristics of the UTC Power PureCell 200 (the former PC25 [2]). This device has been chosen as the reference since it is the sole fuel cell system that has achieved a consistent market penetration.
164
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
η E,T
Q
pFC
fuel cells
ηeFC
QE
ηhFC
absorption chillers
AC
COP'
QC
AC
compression chillers
COPC
boilers
ηB
QpH
hospital
COP
QH
Fig. 1. Scheme of PAFCs retrofit configuration.
The main characteristic of this hybrid plant [15] are: • fuel cell electrical efficiency geFC = 39%, • fuel cell rated power 200 kW for each installed device (no. 2), • average utilization 7000 h/year (19.18 h/day), • fuel cell low enthalpy thermal recoveries efficiency at 120 C ghFC = 17.55%, • absorption chiller COPAC = 0.7 (heat pump COP0AC ¼ 1.7). The fossil energy need related to this option can be evaluated as follows: Qp ¼ QpE þ QpFC þ QpH ;
ð2Þ
where the terms QpE and QpH can be calculated as a function of the fixed total fuel cell rated power by using the following equations (3) for the hot and cold season respectively:
3.3. STS retrofit configuration Solar collectors hybrid plant (STS) shown in Fig. 2. In this scheme, each collector concentrates the sunlight onto the steel pipe located in its focal axis heating a silicone polymer (‘‘organic’’) fluid, flowing inside this pipe. This heated fluid is directly employed as the working fluid in a Rankine power cycle generating electricity. Finally, heat recoveries are used first to feed absorption chillers, secondary to reduce the quote of heating in charge of conventional systems (directly, or indirectly through the scheme: absorption chillers-heat pump). For this analysis the Solel-IND300 collector has been chosen as the reference. In Table 2 the values of the monthly direct radiation ðQ0S Þ and diffuse radiation ðQ00S Þ on a horizontal surface located at Lagosanto are quoted. The main characteristics of this scheme are summarized below [16]:
8 h i 1 > < QpE ¼ g 1 QE QpFC geFC þ COP ðQ Q g COP Þ ; AC C pFC hFC C E;T h i summer > : QpH ¼ g1 QH COP1 max 0; ðQpFC ghFC COPAC QC Þ ; AC B ( 1 QpE ¼ gE;T QE QpFC geFC ; winter QpH ¼ g1B QH QpFC ghFC COP0AC :
ð3Þ
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
165
η E,T
Q's
solar thermal system
η eSTS
QE
η hSTS
absorption chillers
hospital
COP
AC
COP'
QC
AC
compression chillers
COPC
boilers
ηB
QpH
QH
Fig. 2. Scheme of STS retrofit configuration.
Table 2 Monthly direct radiation ðQS0 Þ and diffuse radiation ðQS00 Þ on a horizontal surface (monthly solar collectors efficiency, ghSTS) Month
QS0 [kW h/m2]
QS00 [kW h/m2]
Intense daylight [h/d]
gcSTS (%)
January February March April May June July August September October November December
18.08 31.89 49.08 89.17 115.39 118.33 141.22 105.06 85.00 58.56 16.67 11.19
21.53 28.00 44.78 55.83 66.31 68.33 64.58 60.28 45.00 33.58 22.50 18.08
2.8 3.6 4.7 6.2 7.7 8.6 9.6 8.6 7.0 4.8 2.0 2.0
1.11 8.78 22.82 24.11 39.00 46.14 47.74 45.59 32.00 8.88 1.80 0.09
• geSTS monthly solar thermal systems electrical efficiency, equal to the product of gORC = 17% and gcSTS (also summarized in Table 2), • absorption chiller COPAC = 0.7 (heat pump COP0AC ¼ 1.7). The fossil energy need related to this option can be evaluated as follows: Qp ¼ QpE þ QpH ;
ð4Þ
where the terms QpE and QpH can be calculated monthly, with the radiation data of Table 2, by means of the following equations (5) for the hot and cold season respectively:
8 h i I 1 > < QpE ¼ g 1 QE QIS geSTS þ COP Q Q g COP ; AC hSTS C S C E;T h i summer > : QpH ¼ g1 QH COP1 max 0;ðQIS ghSTS COPAC QC Þ ; AC B ( I 1 QpE ¼ gE;T ½QE QS geSTS ; winter QpH ¼ g1B QH QIS ghSTS COP0AC :
ð5Þ
166
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
Q's+ Q''s
QE
η E,T
photovoltaic system
η PV
compression chillers
QpH boilers
ηB
COPC
QC hospital
QH
Fig. 3. Scheme of PVS retrofit configuration.
3.4. PVS retrofit configuration Photovoltaic hybrid plant (PVS) shown in Fig. 3: this option consists of the ‘‘conventional’’ plant integrated by photovoltaic cells. The Helios H1000 photovoltaic module has been selected as the reference system. The basic characteristics of the PV hybrid plant are: • photovoltaic modules efficiency gPV = 12%, • a balance-of-system (BOS) efficiency (gBOS) equal to 80%. The fossil energy need Qp related to this option can be evaluated as sum of the terms QpE and QpH. In this case, these terms can be calculated monthly, with the radiation data of Table 2, by means of the following equations: 8 h i < QpE ¼ 1 QE ðQI þ QII ÞgPV þ QC ; S S gE;T COPC ð6Þ : Q ¼ QH : pH gB The operations of the selected plants have been investigated in two plant size-variable scenarios in which the plants have been sized in accordance with the abovementioned constraints. The amount of electricity production and, obviously, the solar field size in the STS and PVS also depend on solar radiation available at the place chosen as the model site. In this condition, on the basis of the monthly direct Q0S and diffuse Q00S solar radiation available at Lagosanto (Table 2), the dimensions of the solar fields have been calculated in order to have the same electricity self-production of no. 1 PAFC (200 kW: scenario no. 1) or no. 2 PAFC (200 kW + 200 kW: scenario no. 2). It has been demonstrated that the STS and PV solar field sizes have to be equal to 13,124 m2 and 4815 m2 respectively in order to produce the same amount of electricity of one PAFC in
July. In the second scenario (2 PAFCs), the former values rise to 26,248 m2 and 9630 m2 respectively for the STS and the PV solar fields.
4. Results The energy criteria adopted to compare the viability of the investigated options are primary fossil energy consumption and greenhouse gas emissions. The comparison between the various scenarios has produced the following results. 4.1. Primary energy consumption From Fig. 4 it is clear that there would be a large reduction in the monthly primary energy consumption in each of the retrofit scenarios here examined. The comparison between the conventional and the hybrid scenarios reveals that, regardless of the scenario of study, the highest reductions would always occur in the high-temperature solar plant configuration (STS). This result is first attributable to the large exploitation of solar renewable energy achieved thanks to the collectors, then, unlike what happens in the PVS hybrid plant, to the abundant availability of thermal recoveries which can be used to lower the boilersÕ use. Fuel cell hybrid plants show a lower reduction since the gas consumption rises significantly. This is due to the choice of feeding fuel cells with natural gas. 4.2. Greenhouse gas reductions The pollutant emissions from each of the selected systems have been evaluated in accordance with the values given in the literature. In all the scenarios the emissions were significantly lowered compared to those from the conventional hospital. This would be mainly due to the utilization of high efficiency systems directly fed by
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169 MWh
tCO2
SCENARIO 1
SCENARIO 1
800
3000
167
600 2000 400 1000 200 BASIC
0
a
PAFC
JAN FEB MAR APR MAY JUN
MWh
STS
BASIC
PVS
JUL AUG SEP OCT NOV DEC
PAFC
a
PVS
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
tCO2
SCENARIO 2
3000
STS
0
SCENARIO 2
800
600 2000 400 1000 200 BASIC
PAFC
STS
PVS
BASIC
0
b
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
PAFC
PVS
STS
0
b
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Fig. 4. Monthly primary energy consumption in the two size-variable cases of study: (a) scenario 1, (b) scenario 2.
Fig. 5. Predicted monthly CO2 emissions in the two size-variable cases of study: (a) scenario 1, (b) scenario 2.
renewable energy sources or characterized by ‘‘clean’’ energy processes. Secondly, the use of heat recovery to fulfill the heating and cooling needs (together with the consequent significant reduction in boiler and compression chiller use) could also considerably enhance pollution reduction. In all the cases the CO2 emissions, associated with the fulfillment of the energy requirements, would significantly decrease as shown in Fig. 5. The trend followed by the other pollutants confirmed the same pattern. High-temperature devices could perform a higher pollutant reduction during summer months but are almost inoperative during the cold season; a fuel cell hybrid plant, instead, could achieve a constant pollution reduction throughout the year. In order to assess the effectiveness in terms of emissions reduction and plant size of the retrofit options here
examined, results have been summarized calculating the yearly specific avoided emissions for each electrical kW h produced from the non-conventional part of the plant (kW he,NC). The predictions are summarized in Table 3. If the plant size does not affect this parameter for the PAFCs and the PVSs hybrid plants, it is interesting to observe that the larger is the STS plant, the higher are the expected specific avoided emissions.
5. Economic analysis Initially, the feasibility of each option has been assessed in terms of annual return, simple payback period and IRR considering investment costs, running costs and avoided costs. The last parameter has been
Table 3 Predicted yearly specific avoided emissions for each electrical kW h produced from the non-conventional part of the plant Scenario of study
Plant configuration
Pollutant CO2
NOx
SO2
Particulates
kg/kW he,NC
g/kW he,NC
g/kW he,NC
g/kW he,NC
Scenario 1
PAFCs STS PVS
0.60 1.01 0.69
0.61 0.82 0.58
0.99 1.22 0.95
0.03 0.11 0.03
Scenario 2
PAFCs STS PVS
0.60 1.08 0.68
0.61 0.88 0.58
0.99 1.29 0.95
0.03 0.13 0.03
0.233* 20* 0.373 57 0.268* 25* 0.470 150 0.060* 5* 0.286 29 0.232* 20* 0.373 57 0.283* 28* 0.287 29 (7 years) IRR SPB
[%] [y]
0.061* 1.395 5* Never
127.5 512.8* 86.5 80.8 183.6* 63.8 17.2 40.4 Total Annual return
[k€/y]
233.9*
237.2*
Denotes computations with externalities.
6. Conclusions
*
393.3 89.3 208.1 193.5* 390.1* 196.6
67.9 77.9 62.3 158.2 31.5 7.0
Electricity self-production Recovered heat (heating) Recovered heat (cooling) Avoided emissions (CO2)* Total Annual savings
[k€/y] [k€/y] [k€/y] [k€/y] [k€/y]
156.2 0.0 156.2 Increase of natural gas needs [k€/y] Maintenance [k€/y] Total [k€/y] Annual running costs
0.0 225.3 225.3
1126.7 40.0 1166.7 Systems costs [k€] Maint. contract (una tantum) [k€] Total [k€] Capital costs
6684.4 0.0 6684.4
254.4* 462.5*
89.3 0.0 0.0
119.8* 209.1*
316.4 62.9 13.9
312.5 0.0 312.5 0.0 25.6 25.6
3651.4 0.0 3651.4
PVS STS
464.3*
178.7
178.7 0.0 0.0 135.7 266.9 66.6
426.3* 895.6*
0.0 51.2 51.2 0.0 382.8 382.8
469.3
7302.8 0.0 7302.8 12,988.7 0.0 12,988.7 2243.3 80.0 2323.3
PAFC PAFC
383.6* 776.8*
PVS STS Scenario 2 Scenario 1
The main results obtained are summarized in Table 4. It is interesting to detect that in all the cases considered here the IRR assumes a negative value and even the simple payback period (SPB) is much longer than the expected life of the systems. At the moment, for these reasons, the viability of these hybrid plants is strictly dependent on the availability of public funds or specific government actions. However it is important to highlight that only costs associated with energy processes have been considered in this first computation session. In fact, even though it is not mandatory and no certain assertions can be made about the respect of the deterministic principle, it is interesting to repeat the former computations also considering the amount of hidden cost savings associated to externalities (e.g. 0.22 €/ kg CO2 emitted: data elaborated from ExternE National Implementation Italy [12]). In this case the avoided pollutant emissions can be transformed into a positive annual return completely changing the economic scenarios. Results, quoted in italic with superscript *, in Table 4 confirm that the consideration of externalities has the potential to change the previous conclusions shifting the balance towards the use of these new technologies.
Costs element
Unit
computed at the seventh year of life for each hybrid plant. This choice has been made considering that fuel cells have the shortest expected life (7 years) among the selected systems. Both the investment and the maintenance costs were evaluated according to the information obtained from the manufacturers [15,16]. The annual interest rate has been assumed at 3% while Italian taxes and/or fiscal incentives were not considered, in order to achieve the most general results as possible. The following data were also considered in the analysis: • electricity cost: 0.113 €/kW h, • natural gas: 0.413 €/S m3 for conventional systems.
Costs type
Table 4 Economic analysis
363.7*
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
236.2* 414.9*
168
This paper develops a theoretical analysis of the feasibility of a hybrid plant applied to a real hospital located in Ferrara (Italy). The solutions here assessed consider the use of high efficiency systems directly fed by renewable energy sources or characterized by ‘‘clean’’ energy processes. Three retrofit configurations have been analysed: PAFC, STS and PV hybrid plants. The main constraint that has been respected concerns the sizing of the plants being related to the minimum modular size of 200 kW usually characterizing PAFC devices. It has been stated that the electricity ‘‘self-production’’ in July from the ‘‘non-conventional’’ part of the
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
solar plants should equal the production that could be achieved from a PAFCs plant with a number of fuel cells up to two. The energy performance of the hybrid plants has been always evaluated considering as a benchmark the conventional systems operating today in the medical center. The prediction of the yearly primary energy consumptions revealed consistent savings in all the cases investigated. The major primary energy savings occurred in the STS hybrid plant configurations. The results show that, in all the cases, these retrofit policies could offer a significant greenhouse gas emission reduction. PAFC hybrid plants, in particular (thanks to the continuity of their operation) could ensure a constant pollutant reduction throughout a whole year, while STS hybrid plants would concentrate their benefits in terms of pollution abatement especially during summer. The economic analysis has confirmed that today the cost of these devices still represents an insurmountable market barrier (negative IRR, unattainable simple payback period). Were the previous economic computations to be repeated, also considering the hidden costs associated with externalities (even if the assessment of these costs is still open to interpretation) in terms of avoided pollutant emissions, the results would change considerably in favor of the technologies being examined here. Perhaps, the considerable energy savings and the pollutant emission reductions, that could be achieved by upgrading conventional systems to those of the considered hybrid plants, should persuade the national boards to enhance their support towards business development of these new technologies, as long as they consolidate firm market penetration.
References [1] Common position (EC) No. 46/2002 on the energy performance of buildings, Official Journal of the European Communities, 7 June 2002.
169
[2] G. Bizzarri, G.L. Morini, Greenhouse gas reduction and primary energy savings via adopting of a fuel cells hybrid plant in a hospital, Applied Thermal Engineering 24 (2) (2004) 383–400. [3] A.W.M. Van Schijndel, Optimal operation of a hospital power plant, Energy and Buildings 34 (10) (2002) 1055–1065. [4] Y. Ying, E.J. Hu, Thermodynamic advantages of using solar energy in the regenerative Rankine power plant, Applied Thermal Engineering 19 (11) (1999) 1173–1180. [5] R.J. Spiegel, D.L. Greenberg, E.C. Kern, D.E. House, Emission reduction data for grid-connected photovoltaic power systems, Solar Energy 68 (5) (2000) 475–485. [6] S. Krauter, A.R. Ruther, Considerations for the calculation of greenhouse gas reduction by photovoltaic solar energy, Renewable Energy 29 (3) (2004) 345–355. [7] J.L. Gomez-Amo, F. Tena, J.A. Martınez-Lozano, M.P. Utrillas, Energy saving and solar energy use in the University of Valencia (Spain), Renewable Energy 29 (5) (2004) 675–685. [8] A. Ferguson, V.I. Ugursal, Fuel cell modelling for building cogeneration applications, Journal of Power Sources 137 (1) (2004) 30–42. [9] G. Bizzarri, Il fabbisogno energetico in ospedale. Indagine sui fabbisogni di energia elettrica in alcune strutture ospedaliere della provincia di Ferrara, Tecnica Ospedaliera 31 (8) (2001) 76–82 (in Italian). [10] G. Bizzarri, Analisi Energetica di Complessi Ospedalieri, PhD thesis, Universita` di Ferrara, Ferrara, 2003, Available from:, last accessed 1/1/2005 (in Italian). [11] G. Bizzarri, G.L. Morini, Greenhouse gas reductions and primary energy savings via adoption of hybrid plants in place of conventional ones, in: Proceedings of Air Pollution XII, Twelfth International Conference on Modelling, Monitoring and Management of Air Pollution, Rhodes, Greece, Witt Press, Southampton, Boston, 2004, pp. 327–337. [12] ExternE (Externalities of Energy) National Implementation: Italy, Final Report, October 1997; European Commissions, DirectorateGeneral XII, Science Research and Development, Available from: , last accessed 1/1/2005. [13] GRTN, Annual Report and Accounts: 2002, Available from: , last accessed 1/1/2005. [14] M. Dentice DÕAccadia, M. Sasso, S. Sibilio, R. Vanoli, Applicazioni di Energetica, Liguori, Napoli, 1999 (in Italian). [15] G. Marcenaro, Ansaldo Fuel Cells, Genova, Italy, Available from: , February 2004 (Personal communication). [16] Z. Santini, Baxter Engineering, Perugia, Italy, Available from: , February 2004 (Personal communication).
New technologies for an effective energy retrofit of hospitals Giacomo Bizzarri a
a,*
, Gian Luca Morini
b
Dipartimento di Architettura, Universita` degli Studi di Ferrara, Via Quartieri, 8-44100 Ferrara, Italy b DIENCA, Universita` degli Studi di Bologna, Viale Risorgimento, 2-40136 Bologna, Italy Received 13 March 2005; accepted 26 May 2005 Available online 18 July 2005
Abstract Following the approval by the European Parliament of the directive on energy efficiency of public buildings, a great effort has been directed towards enhancing low-emission systems such as fuel cells (FC), photovoltaic systems (PVS) or solar thermal systems (STS), especially in all public facilities, such as hospitals, characterized by relevant energy requirements. This paper develops a theoretical analysis which focuses on the environmental benefits achievable through a shift from the conventional systems, normally operating in hospitals, to various hybrid plants. The model site is a hospital located near Ferrara (Italy). Several hybrid schemes were investigated and compared: PAFCs (phosporic acid fuel cells), STS and PVS. An energy analysis was developed for each option assuming, as a benchmark, the conventional systems operating today in the medical center. The results, presented with reference to the primary energy requirements and the pollutant emissions, demonstrate that in the case of existing systems being upgraded with these hybrid plants, overall emissions could be abated with a significant reduction in fossil energy consumption. Finally, an economic study, even taking external factors into account, is developed for all the retrofit scenarios in terms of annual return, simple payback period and IRR. 2005 Elsevier Ltd. All rights reserved. Keywords: Hybrid plants; Pollutant reductions; Primary energy savings; Fuel cells; Solar thermal systems; Photovoltaic systems
1. Introduction Theoretically, local governments have the potential to control, both directly and indirectly, a considerable amount of the greenhouse gases (GHGs) emitted, originated from the heating and cooling plants of public buildings (local government premises, hospitals, etc.) as well as from the supply of basic services such as transportation, water and waste management. Recently, the
Abbreviation: IRR, Internal rate of return. Corresponding author. Tel.: +39 0532 293653; fax: +39 0532 293627. E-mail addresses: [email protected] (G. Bizzarri), gianluca. [email protected] (G.L. Morini). *
1359-4311/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2005.05.015
European Parliament unanimously approved the proposed directive on energy efficiency of public buildings, whose objective is the control and reduction of energy consumption by 22% by the year 2010 [1]. One example of a simple, useful tool that local governments can harness in order to reduce GHG emissions in a meaningful way is to upgrade their buildingsÕ plants (municipalities, hospitals, decisional centers) with a shift away from the use of conventional fossil fuels toward more ecological, renewable energy sources. These technologies produce environmental benefits since non-renewable energy can be preserved and environmental pollution can be drastically reduced. In addition to this, the decentralization of the electricity production plants mitigates the grid distribution losses. In recent years, several studies have been developed in this field. Bizzarri and Morini [2] proved that
162
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
Nomenclature COPC compression chillers coefficient of performance COPAC absorption chillers coefficient of performance COP0AC absorption chillers (heat pump mode) coefficient of performance QC monthly cooling requirement (MW h) QE monthly electrical requirement except from electricity for compression chiller end use (MW h) E Q monthly electrical requirement (MW h) QH monthly heating requirement (MW h) Qp monthly primary fossil energy requirements (MW h) QpE monthly primary fossil energy requirements associated to thermo-electric power plant operation (MW h) QpFC fuel cells monthly primary fossil energy requirements (MW h) QpH monthly primary fossil energy requirements associated to boilers operation (MW h) Q0S monthly direct radiation at Lagosanto (lat. 44.5, lon. 12.1) (kW h/m2)
harnessing a fuel cell hybrid plant in a hospital can bring substantial primary energy savings, as well as a consistent drop in pollutant emissions. Van Schijndel [3] showed how the optimization of the primary energy consumption associated with the hospitalsÕ thermal plants operation can be compatible with the constraint of a positive economic profit. Ying and Hu [4] demonstrated that the use of solar energy is of great importance in reducing GHG emissions by analyzing a solar aided plant where solar heat is used to replace the extracted steam to heat the feedwater in the regenerative Rankine plant. Spiegel et al. [5], Krauter and Ruther [6], Gomez-Amo et al. [7] studied the potential of photovoltaic systems in terms of emission reduction. Recently, Ferguson and Ugursal [8] investigated the effect of varying fuel cells size on the performance of cogeneration systems. This paper is devoted to investigate the real opportunities in terms of primary energy and money savings and environmental benefits offered by the energy retrofit of a typical Italian hospital. The retrofit policies taken into consideration here consist in a shift from a conventional plant configuration (normally operating in the hospitals), to different hybrid schemes, as phosphoric acid fuel cells (PAFCs), solar thermal systems (STS) and photovoltaic systems (PVS). The hospital of Lagosanto, near Ferrara (Italy), has been chosen as a case study to test the efficacy of these retrofit strategies.
Q00S
monthly diffuse radiation at Lagosanto, (lat. 44.5, lon. 12.1) (kW h/m2)
Greek symbols gB gas-fired boilers thermal efficiency gcSTS monthly collectors efficiency, part of monthly direct radiation transferable into thermal energy by solar collectors gE,T public utility mean electrical efficiency geFC fuel cells electrical efficiency geSTS monthly solar thermal systems electrical efficiency ghFC fuel cell low enthalpy thermal recoveries efficiency ghSTS monthly solar thermal systems low enthalpy thermal recoveries efficiency gORC organic Rankine cycle efficiency gPV monthly photovoltaic systems electrical efficiency
2. Constraints of retrofit The energy requirements of the Lagosanto hospital have been determined according to the same procedures defined in previous studies [2,9,10] and are quoted in Table 1. Examination of Table 1 shows that the monthly electricity demand during summer grows significantly following a common pattern which distinguishes many north Italian hospitals [9]. This growth is due to the high utilization of compression chillers supporting the HVAC systems during the hot season. A peak cut policy, pursuing the optimization of the electrical requireTable 1 E Þ, heating (QH) and cooling (QC) Estimated monthly electrical ðQ demands of LagosantoÕs hospital Month
E [MW he] Q
QH [MW ht]
QC [MW ht]
January February March April May June July August September October November December
475.6 475.5 505.2 480.6 537.4 669.2 689.7 711.3 496.2 517.7 493.4 488.3
1714.5 1448.8 1269.8 893.9 460.3 232.4 134.3 138.9 232.6 636.8 1167.1 1600.2
– – – – 154.2 322.2 533.1 468.2 291.5 – – –
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
ments around the monthly values normally experienced during the colder months, could even produce financial benefits, given that the contracts with the electricity companies tend to be set to the peak of consumption. In this regard, solar technologies are well suited to peak cut purpose since these systems achieve their peak of production in accordance with peak demand during the hottest sunny days of the summer [10,11]. It has been proved that, for hybrid solar thermal power plants, the major fossil energy saving and reduction of greenhouse gases are obtained when the solar collectors provide an amount of electricity consistent with the summer growth of consumption [10]. Today, in the hospital of Lagosanto, heat and power requirements are provided by ‘‘conventional’’ systems. Electricity is imported from the grid whereas heating is completely supplied by gas-fired boilers. Compression chillers satisfy cooling needs. The retrofit scenarios presented in this article have been developed considering two main constraints. The first constraint is linked to plant size. A previous study [11] demonstrated that a plant sized in such a way that the monthly electricity ‘‘self-production’’ from the ‘‘non-conventional’’ part of the plant was equal to the gap that existed between the average monthly electricity requirement characteristic of summer months (from June to August) and that typical of other months brought considerable environmental benefits, but was shown not to be economically sustainable. With cost effectiveness being a basic target, it appeared interesting to look into both energy and economic analysis finally taking into account also externalities [12] and introducing a second case study consisting of a smaller plant. If the photovoltaic and solar thermal systems allow plants of varying sizes to be built, the PAFCs, chosen as the reference being the sole ones with sufficiently reliable data in the literature, are on the market in plants not smaller than 200 kW. This substantial difference has imposed as the main constraint that plant sizes had to be somehow linked to the market availability of PAFCs. It means system sizes could not be less than 200 kW. In particular, plant configurations were studied that would guarantee a production of electrical energy equivalent to that which would have been able to be achieved with an installation of up to 2 PAFCs. The following assumptions have also been taken into account. • Trigeneration is pursued: if low enthalpy heat recoveries are available they are used first to feed absorption chillers for cooling (only in summer), then to mitigate boiler operations (directly or indirectly, making absorption chillers work as heat pumps during the cold season).
163
• Absorption chillers are sized in such a way as to always be fed by the whole of the energy recoveries when these are available. • In the peak mode, the energy needs in deficit is supplied by the ‘‘conventional’’ systems: electricity is imported from the grid, heat and cold are generated respectively using gas-fired boilers and compression chillers. • Electricity from the grid is assumed to have been derived from a oil fired power station [13]. • The heat loss in the plant network is disregarded.
3. Plant configurations Four different plant configurations were investigated:
3.1. Basic configuration In this scheme, the following numerical values have been adopted: • public utility mean electrical efficiency gE,T = 39% [13,14], • gas-fired boilers seasonal thermal efficiency gB = 85%, • compression chiller COPC = 3.0. The monthly primary fossil energy requirements associated to the fulfillment of the whole of the hospitalÕs energy needs can be evaluated according to the following energy balance:
Qp ¼ QpE þ QpH ¼ ¼
1 gE;T
QE þ
QC Q þ H COPC gB
E QH Q þ . gE;T gB
ð1Þ
3.2. PAFC retrofit configuration Phosphoric acid fuel cells (PAFCs) hybrid plant shown in Fig. 1: the ‘‘non-conventional’’ part of the plant consists in PAFCs also integrated with an absorption cooling system. The heating is supplied partially by heat recoveries from the fuel cell and the remainder by gas-fired boilers. The fuel cells here investigated meet the characteristics of the UTC Power PureCell 200 (the former PC25 [2]). This device has been chosen as the reference since it is the sole fuel cell system that has achieved a consistent market penetration.
164
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
η E,T
Q
pFC
fuel cells
ηeFC
QE
ηhFC
absorption chillers
AC
COP'
QC
AC
compression chillers
COPC
boilers
ηB
QpH
hospital
COP
QH
Fig. 1. Scheme of PAFCs retrofit configuration.
The main characteristic of this hybrid plant [15] are: • fuel cell electrical efficiency geFC = 39%, • fuel cell rated power 200 kW for each installed device (no. 2), • average utilization 7000 h/year (19.18 h/day), • fuel cell low enthalpy thermal recoveries efficiency at 120 C ghFC = 17.55%, • absorption chiller COPAC = 0.7 (heat pump COP0AC ¼ 1.7). The fossil energy need related to this option can be evaluated as follows: Qp ¼ QpE þ QpFC þ QpH ;
ð2Þ
where the terms QpE and QpH can be calculated as a function of the fixed total fuel cell rated power by using the following equations (3) for the hot and cold season respectively:
3.3. STS retrofit configuration Solar collectors hybrid plant (STS) shown in Fig. 2. In this scheme, each collector concentrates the sunlight onto the steel pipe located in its focal axis heating a silicone polymer (‘‘organic’’) fluid, flowing inside this pipe. This heated fluid is directly employed as the working fluid in a Rankine power cycle generating electricity. Finally, heat recoveries are used first to feed absorption chillers, secondary to reduce the quote of heating in charge of conventional systems (directly, or indirectly through the scheme: absorption chillers-heat pump). For this analysis the Solel-IND300 collector has been chosen as the reference. In Table 2 the values of the monthly direct radiation ðQ0S Þ and diffuse radiation ðQ00S Þ on a horizontal surface located at Lagosanto are quoted. The main characteristics of this scheme are summarized below [16]:
8 h i 1 > < QpE ¼ g 1 QE QpFC geFC þ COP ðQ Q g COP Þ ; AC C pFC hFC C E;T h i summer > : QpH ¼ g1 QH COP1 max 0; ðQpFC ghFC COPAC QC Þ ; AC B ( 1 QpE ¼ gE;T QE QpFC geFC ; winter QpH ¼ g1B QH QpFC ghFC COP0AC :
ð3Þ
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
165
η E,T
Q's
solar thermal system
η eSTS
QE
η hSTS
absorption chillers
hospital
COP
AC
COP'
QC
AC
compression chillers
COPC
boilers
ηB
QpH
QH
Fig. 2. Scheme of STS retrofit configuration.
Table 2 Monthly direct radiation ðQS0 Þ and diffuse radiation ðQS00 Þ on a horizontal surface (monthly solar collectors efficiency, ghSTS) Month
QS0 [kW h/m2]
QS00 [kW h/m2]
Intense daylight [h/d]
gcSTS (%)
January February March April May June July August September October November December
18.08 31.89 49.08 89.17 115.39 118.33 141.22 105.06 85.00 58.56 16.67 11.19
21.53 28.00 44.78 55.83 66.31 68.33 64.58 60.28 45.00 33.58 22.50 18.08
2.8 3.6 4.7 6.2 7.7 8.6 9.6 8.6 7.0 4.8 2.0 2.0
1.11 8.78 22.82 24.11 39.00 46.14 47.74 45.59 32.00 8.88 1.80 0.09
• geSTS monthly solar thermal systems electrical efficiency, equal to the product of gORC = 17% and gcSTS (also summarized in Table 2), • absorption chiller COPAC = 0.7 (heat pump COP0AC ¼ 1.7). The fossil energy need related to this option can be evaluated as follows: Qp ¼ QpE þ QpH ;
ð4Þ
where the terms QpE and QpH can be calculated monthly, with the radiation data of Table 2, by means of the following equations (5) for the hot and cold season respectively:
8 h i I 1 > < QpE ¼ g 1 QE QIS geSTS þ COP Q Q g COP ; AC hSTS C S C E;T h i summer > : QpH ¼ g1 QH COP1 max 0;ðQIS ghSTS COPAC QC Þ ; AC B ( I 1 QpE ¼ gE;T ½QE QS geSTS ; winter QpH ¼ g1B QH QIS ghSTS COP0AC :
ð5Þ
166
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
QpE
public utility
Q's+ Q''s
QE
η E,T
photovoltaic system
η PV
compression chillers
QpH boilers
ηB
COPC
QC hospital
QH
Fig. 3. Scheme of PVS retrofit configuration.
3.4. PVS retrofit configuration Photovoltaic hybrid plant (PVS) shown in Fig. 3: this option consists of the ‘‘conventional’’ plant integrated by photovoltaic cells. The Helios H1000 photovoltaic module has been selected as the reference system. The basic characteristics of the PV hybrid plant are: • photovoltaic modules efficiency gPV = 12%, • a balance-of-system (BOS) efficiency (gBOS) equal to 80%. The fossil energy need Qp related to this option can be evaluated as sum of the terms QpE and QpH. In this case, these terms can be calculated monthly, with the radiation data of Table 2, by means of the following equations: 8 h i < QpE ¼ 1 QE ðQI þ QII ÞgPV þ QC ; S S gE;T COPC ð6Þ : Q ¼ QH : pH gB The operations of the selected plants have been investigated in two plant size-variable scenarios in which the plants have been sized in accordance with the abovementioned constraints. The amount of electricity production and, obviously, the solar field size in the STS and PVS also depend on solar radiation available at the place chosen as the model site. In this condition, on the basis of the monthly direct Q0S and diffuse Q00S solar radiation available at Lagosanto (Table 2), the dimensions of the solar fields have been calculated in order to have the same electricity self-production of no. 1 PAFC (200 kW: scenario no. 1) or no. 2 PAFC (200 kW + 200 kW: scenario no. 2). It has been demonstrated that the STS and PV solar field sizes have to be equal to 13,124 m2 and 4815 m2 respectively in order to produce the same amount of electricity of one PAFC in
July. In the second scenario (2 PAFCs), the former values rise to 26,248 m2 and 9630 m2 respectively for the STS and the PV solar fields.
4. Results The energy criteria adopted to compare the viability of the investigated options are primary fossil energy consumption and greenhouse gas emissions. The comparison between the various scenarios has produced the following results. 4.1. Primary energy consumption From Fig. 4 it is clear that there would be a large reduction in the monthly primary energy consumption in each of the retrofit scenarios here examined. The comparison between the conventional and the hybrid scenarios reveals that, regardless of the scenario of study, the highest reductions would always occur in the high-temperature solar plant configuration (STS). This result is first attributable to the large exploitation of solar renewable energy achieved thanks to the collectors, then, unlike what happens in the PVS hybrid plant, to the abundant availability of thermal recoveries which can be used to lower the boilersÕ use. Fuel cell hybrid plants show a lower reduction since the gas consumption rises significantly. This is due to the choice of feeding fuel cells with natural gas. 4.2. Greenhouse gas reductions The pollutant emissions from each of the selected systems have been evaluated in accordance with the values given in the literature. In all the scenarios the emissions were significantly lowered compared to those from the conventional hospital. This would be mainly due to the utilization of high efficiency systems directly fed by
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169 MWh
tCO2
SCENARIO 1
SCENARIO 1
800
3000
167
600 2000 400 1000 200 BASIC
0
a
PAFC
JAN FEB MAR APR MAY JUN
MWh
STS
BASIC
PVS
JUL AUG SEP OCT NOV DEC
PAFC
a
PVS
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
tCO2
SCENARIO 2
3000
STS
0
SCENARIO 2
800
600 2000 400 1000 200 BASIC
PAFC
STS
PVS
BASIC
0
b
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
PAFC
PVS
STS
0
b
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Fig. 4. Monthly primary energy consumption in the two size-variable cases of study: (a) scenario 1, (b) scenario 2.
Fig. 5. Predicted monthly CO2 emissions in the two size-variable cases of study: (a) scenario 1, (b) scenario 2.
renewable energy sources or characterized by ‘‘clean’’ energy processes. Secondly, the use of heat recovery to fulfill the heating and cooling needs (together with the consequent significant reduction in boiler and compression chiller use) could also considerably enhance pollution reduction. In all the cases the CO2 emissions, associated with the fulfillment of the energy requirements, would significantly decrease as shown in Fig. 5. The trend followed by the other pollutants confirmed the same pattern. High-temperature devices could perform a higher pollutant reduction during summer months but are almost inoperative during the cold season; a fuel cell hybrid plant, instead, could achieve a constant pollution reduction throughout the year. In order to assess the effectiveness in terms of emissions reduction and plant size of the retrofit options here
examined, results have been summarized calculating the yearly specific avoided emissions for each electrical kW h produced from the non-conventional part of the plant (kW he,NC). The predictions are summarized in Table 3. If the plant size does not affect this parameter for the PAFCs and the PVSs hybrid plants, it is interesting to observe that the larger is the STS plant, the higher are the expected specific avoided emissions.
5. Economic analysis Initially, the feasibility of each option has been assessed in terms of annual return, simple payback period and IRR considering investment costs, running costs and avoided costs. The last parameter has been
Table 3 Predicted yearly specific avoided emissions for each electrical kW h produced from the non-conventional part of the plant Scenario of study
Plant configuration
Pollutant CO2
NOx
SO2
Particulates
kg/kW he,NC
g/kW he,NC
g/kW he,NC
g/kW he,NC
Scenario 1
PAFCs STS PVS
0.60 1.01 0.69
0.61 0.82 0.58
0.99 1.22 0.95
0.03 0.11 0.03
Scenario 2
PAFCs STS PVS
0.60 1.08 0.68
0.61 0.88 0.58
0.99 1.29 0.95
0.03 0.13 0.03
0.233* 20* 0.373 57 0.268* 25* 0.470 150 0.060* 5* 0.286 29 0.232* 20* 0.373 57 0.283* 28* 0.287 29 (7 years) IRR SPB
[%] [y]
0.061* 1.395 5* Never
127.5 512.8* 86.5 80.8 183.6* 63.8 17.2 40.4 Total Annual return
[k€/y]
233.9*
237.2*
Denotes computations with externalities.
6. Conclusions
*
393.3 89.3 208.1 193.5* 390.1* 196.6
67.9 77.9 62.3 158.2 31.5 7.0
Electricity self-production Recovered heat (heating) Recovered heat (cooling) Avoided emissions (CO2)* Total Annual savings
[k€/y] [k€/y] [k€/y] [k€/y] [k€/y]
156.2 0.0 156.2 Increase of natural gas needs [k€/y] Maintenance [k€/y] Total [k€/y] Annual running costs
0.0 225.3 225.3
1126.7 40.0 1166.7 Systems costs [k€] Maint. contract (una tantum) [k€] Total [k€] Capital costs
6684.4 0.0 6684.4
254.4* 462.5*
89.3 0.0 0.0
119.8* 209.1*
316.4 62.9 13.9
312.5 0.0 312.5 0.0 25.6 25.6
3651.4 0.0 3651.4
PVS STS
464.3*
178.7
178.7 0.0 0.0 135.7 266.9 66.6
426.3* 895.6*
0.0 51.2 51.2 0.0 382.8 382.8
469.3
7302.8 0.0 7302.8 12,988.7 0.0 12,988.7 2243.3 80.0 2323.3
PAFC PAFC
383.6* 776.8*
PVS STS Scenario 2 Scenario 1
The main results obtained are summarized in Table 4. It is interesting to detect that in all the cases considered here the IRR assumes a negative value and even the simple payback period (SPB) is much longer than the expected life of the systems. At the moment, for these reasons, the viability of these hybrid plants is strictly dependent on the availability of public funds or specific government actions. However it is important to highlight that only costs associated with energy processes have been considered in this first computation session. In fact, even though it is not mandatory and no certain assertions can be made about the respect of the deterministic principle, it is interesting to repeat the former computations also considering the amount of hidden cost savings associated to externalities (e.g. 0.22 €/ kg CO2 emitted: data elaborated from ExternE National Implementation Italy [12]). In this case the avoided pollutant emissions can be transformed into a positive annual return completely changing the economic scenarios. Results, quoted in italic with superscript *, in Table 4 confirm that the consideration of externalities has the potential to change the previous conclusions shifting the balance towards the use of these new technologies.
Costs element
Unit
computed at the seventh year of life for each hybrid plant. This choice has been made considering that fuel cells have the shortest expected life (7 years) among the selected systems. Both the investment and the maintenance costs were evaluated according to the information obtained from the manufacturers [15,16]. The annual interest rate has been assumed at 3% while Italian taxes and/or fiscal incentives were not considered, in order to achieve the most general results as possible. The following data were also considered in the analysis: • electricity cost: 0.113 €/kW h, • natural gas: 0.413 €/S m3 for conventional systems.
Costs type
Table 4 Economic analysis
363.7*
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
236.2* 414.9*
168
This paper develops a theoretical analysis of the feasibility of a hybrid plant applied to a real hospital located in Ferrara (Italy). The solutions here assessed consider the use of high efficiency systems directly fed by renewable energy sources or characterized by ‘‘clean’’ energy processes. Three retrofit configurations have been analysed: PAFC, STS and PV hybrid plants. The main constraint that has been respected concerns the sizing of the plants being related to the minimum modular size of 200 kW usually characterizing PAFC devices. It has been stated that the electricity ‘‘self-production’’ in July from the ‘‘non-conventional’’ part of the
G. Bizzarri, G.L. Morini / Applied Thermal Engineering 26 (2006) 161–169
solar plants should equal the production that could be achieved from a PAFCs plant with a number of fuel cells up to two. The energy performance of the hybrid plants has been always evaluated considering as a benchmark the conventional systems operating today in the medical center. The prediction of the yearly primary energy consumptions revealed consistent savings in all the cases investigated. The major primary energy savings occurred in the STS hybrid plant configurations. The results show that, in all the cases, these retrofit policies could offer a significant greenhouse gas emission reduction. PAFC hybrid plants, in particular (thanks to the continuity of their operation) could ensure a constant pollutant reduction throughout a whole year, while STS hybrid plants would concentrate their benefits in terms of pollution abatement especially during summer. The economic analysis has confirmed that today the cost of these devices still represents an insurmountable market barrier (negative IRR, unattainable simple payback period). Were the previous economic computations to be repeated, also considering the hidden costs associated with externalities (even if the assessment of these costs is still open to interpretation) in terms of avoided pollutant emissions, the results would change considerably in favor of the technologies being examined here. Perhaps, the considerable energy savings and the pollutant emission reductions, that could be achieved by upgrading conventional systems to those of the considered hybrid plants, should persuade the national boards to enhance their support towards business development of these new technologies, as long as they consolidate firm market penetration.
References [1] Common position (EC) No. 46/2002 on the energy performance of buildings, Official Journal of the European Communities, 7 June 2002.
169
[2] G. Bizzarri, G.L. Morini, Greenhouse gas reduction and primary energy savings via adopting of a fuel cells hybrid plant in a hospital, Applied Thermal Engineering 24 (2) (2004) 383–400. [3] A.W.M. Van Schijndel, Optimal operation of a hospital power plant, Energy and Buildings 34 (10) (2002) 1055–1065. [4] Y. Ying, E.J. Hu, Thermodynamic advantages of using solar energy in the regenerative Rankine power plant, Applied Thermal Engineering 19 (11) (1999) 1173–1180. [5] R.J. Spiegel, D.L. Greenberg, E.C. Kern, D.E. House, Emission reduction data for grid-connected photovoltaic power systems, Solar Energy 68 (5) (2000) 475–485. [6] S. Krauter, A.R. Ruther, Considerations for the calculation of greenhouse gas reduction by photovoltaic solar energy, Renewable Energy 29 (3) (2004) 345–355. [7] J.L. Gomez-Amo, F. Tena, J.A. Martınez-Lozano, M.P. Utrillas, Energy saving and solar energy use in the University of Valencia (Spain), Renewable Energy 29 (5) (2004) 675–685. [8] A. Ferguson, V.I. Ugursal, Fuel cell modelling for building cogeneration applications, Journal of Power Sources 137 (1) (2004) 30–42. [9] G. Bizzarri, Il fabbisogno energetico in ospedale. Indagine sui fabbisogni di energia elettrica in alcune strutture ospedaliere della provincia di Ferrara, Tecnica Ospedaliera 31 (8) (2001) 76–82 (in Italian). [10] G. Bizzarri, Analisi Energetica di Complessi Ospedalieri, PhD thesis, Universita` di Ferrara, Ferrara, 2003, Available from: