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Setting a new standard
BIPV
SETTING A NEW STANDARD Zero Energy Homes in the US The United States is undergoing an unprecedented boom in new air conditioning is a standard feature in all home construction. California and its capital Sacramento have new homes built in Sacramento and a major factor in SMUD's peak electrical demand been a part of that boom with record numbers of new homes growth. SMUD is participating in the ZEH built in the last few years. This boom in new home construction initiative because the District believes ZEH is leading to increased demand for electricity, raising utility bills can reduce its peak demand while dramatiand taxing local electrical utility systems. Solar PV is playing a cally reducing new homeowners' utility bills. major role in meeting electricity demand in the region. Mike Keesee, Sacramento Municipal Utility District reports. The SMUD Zero Energy
Home
O
ne of the major appeals of photovoltaic energy is its ability to transform new homes into miniature power plants. Installing a solar electric system on a new home with advanced energyefficiency features creates the potential of home that generates nearly as much electricity as it consumes on an annual basis. This is the promise of a "Zero Energy Home (ZEH)." Since 2003, the Sacramento Municipal Utility District (SMUD), which is the customer-owned electricity provider in
Sacramento, has been working with the U.S. Department of Energy's (DOE) Building American program to encourage local production home builders to build (and sell) ZEHs. DOE's ZEH initiative combines state-of-the art, energy-efficient construction and appliances with commercially available renewable energy systems such as solar electricity. DOE's goal is to help builders create homes that produce as much energy as they use over the course of a year and reduce a new home's total energy bill, electric and gas, by at least 60%. Central
SMUD leads a collaborative effort between the US DOE, the National Renewable Energy Laboratory (NREL), ConSol (DOE's ZEH consultant) and major PV manufacturers, including GE Energy and BP Solar, in working with local new homebuilders to build the ZEHs in the region, including the first all ZEH community at Premier Gardens. The first step in designing a ZEH is to dramatically reduce a home's overall energy use. This enables the homebuilder to install a smaller photovoltaic system to meet the home's electrical needs and, more importantly, helps to reduce the ZEH's overall costs. ConSol put together a package of energy efficiency measures that helped reduce the ZEH's heating and water heating energy use by over 15% and cooling energy use by 50% compared to California's stringent Title-24 building energy standards. A typical ZEH built in Sacramento About the author Mike Keesee is the project manager for the Sacramento Municipal Utility District's (SMUD)'s Zero Energy Home program. He has also managed the SMUD Advantage Home program, the utility's Residential New Construction program. www.smud.org
Figure 1: Premier Gardens Zero Energy Home
26 reFOCUS
July/August 2005
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.
BIPV
Figure 2: GE PV-055 Module (Courtesy of GE Energy)
(Figure 1) includes the following energy efficiency measures: • • • • • •
Low air infiltration Vinyl, low-e, spectrally selective windows 92 percent efficient furnace (AFUE .92) SEER 14 with TXV air conditioner Engineered heating and cooling duct runs Tankless, instantaneous water heater with a .82 Energy Factor • Insulated Hot Water Pipes • Fluorescent Lighting • Third-Party inspection and testing of the home's energy efficiency features, such as the quality of the insulation installation, (qualifying the home as an Energy Star Home). One of the major goals of SMUD's ZEH program is to encourage local homebuilders to adopt newly introduced Roof-Integrated PV (RIPV) products. The first ZEH homes utilized a 2.0 kW AC RIPV system manufactured by GE Energy. The GE Energy solar electric system consists of 48 PV-055 modules (Figure 2) and a SMA "Sunnyboy" 2500 inverter. The system also features a unique "PV" meter supplied by SMUD to record the energy output of the solar system, which is recorded on the homeowner's monthly electric bill. As part of the ZEH research efforts, SMUD is also evaluating the performance of new RIPV products. Of particular concern is whether high roof temperatures will affect RIPV products' performance. SMUD operates its own PV Performance Index. SMUD's PV Performance Index is a software tool developed for evaluating PV system performance based on local, real-time weather data. Weather data is collected from local weather stations and used to estimate PV production based on individual PV system characteristics. This baseline PV Production number is then compared to actual monthly PV system production meter reads. To date,
www.re-focus.net
the GE Energy RIPV system is performing exceptionally well, consistently exceeding 100% of expected kWh production.
ZEH program experience Since 2003, 107 ZEHs have been built in the SMUD service territory. Morrison Homes introduced the first ZEH in Sacramento in 2003 at its Lakeside project where ZEH was offered as an optional upgrade to homebuyers. In 2004, Premier Homes became the first new homebuilder in Sacramento to construct an entire ZEH community called, Premier Gardens. Premier Gardens is a 95unit, "in-fill" project designed for first-time homebuyers. "In-fill" developments are those built inside areas where there already is existing development, rather than in outlying, suburban or "exurban" areas. In-fill developments offer a unique opportunity for middle class families to be closer to work and minimize their commute time. In 2005, a 32unit ZEH project will be built by Treasure Homes (Figure 3).
Energy use and electric bill impacts The Premier Gardens ZEH project offers an unprecedented opportunity for SMUD to compare the impact that ZEH features have on customer's energy use and bills. Adjacent to the Premier Gardens project, a competing homebuilder built 95 similarly sized homes marketed to the same demographic. As a result, the Premier Gardens ZEH energy use, electric peak demand, and utility bills can be compared to the energy use, electric peak demand, and bills of SMUD customers living in the adjoining non-ZEH homes. Data collected for the first ten months of occupancy indicate that residences living in ZEHs use less electricity and have lower electricity bills than those living in homes with enhanced energy efficiency measures only. On average, Premier Gardens
homeowners used 16 percent less electricity than those living in the non-ZEH homes: 5,260 kWh versus 6,252 kWh (Figure 4). The PV systems in the Premier Garden ZEHs are supplying more than 47 percent of the electricity used in the home, 2,498 kWh of the total 5,260 kWh consumed. Over the same 10-month period Premier Gardens homeowners average monthly electric bills were 54 percent lower than the Cresleigh homeowners, $30.48 versus $65.80 and 58% lower than the average monthly SMUD Residential gas-heated customer bill, $73.06 versus $25.89. A closer look at the individual customers' April bills shows the impact a ZEH has on reducing a customer's electric bill. For this period, the ZEHs' average electric bill was 78% lower than the typical SMUD bill and 63% lower than the neighbouring homes right across the street.
Peak demand impact More than 70 percent of SMUD's electric demand growth is driven by new homes (40 MW of the 56 MW of peak load growth in 2003 compared to 2002). The District's system load profile nearly matches the average new home's load profile on the system's peak day (July 22, 2003), confirming the contribution of new homes' load to setting coincident peak electrical demand. Data collected from a sample of 30 SMUD customers participating in the PV Pioneer retrofit and Solar Advantage Home PV programs indicate that PV systems can reduce a home's peak electrical demand by as much as 13 percent (0.4 kW). Figure 5 shows the impact that a PV system has on a
Figure 3: Premier Gardens ZEH Community 95 Zero Energy Homes with 2 kW Solar Systems
July/August 2005
reFOCUS 27
BIPV
Garden ZEH homes will have on customer electrical usage, bills, and peak demand, or the District's electric system. SMUD will conduct whole house monitoring of the ZEH homes in Premier Gardens and the adjacent subdivision for two years. Electrical usage, bills, and peak demand data will be gathered from eighteen homes from each housing development and compared. In addition, solar system performance will be tracked in the Premier ZEHs and correlated with the homes' peak demand to determine the impact ZEH solar systems have on the District's system peak. As data are collected from these homes, a clearer picture of the impact ZEHs have on electrical consumption and peak demand will be reported. Figure 4: ZEH Monthly Average kWh Usage Premier vs. Cresleigh
customer's net electrical demand in July. The top line represents the hourly electric load for a PV customer. The bottom line shows the PV customer's net load, or the amount of electricity supplied by SMUD. The difference between the two lines is made up by the customer's PV system generation. Similarly, comparing an average new home's load to its PV output illustrates the potential for reducing a new home's peak demand. Figure 6 shows the impact a southwestern-oriented 2 kW AC PV system would have on reducing the average new home's peak demand. In this example, the home's peak demand which occurred at 6 p.m. is reduced by 20 percent (0.9 kW). Combining high efficiency measures, such as SEER 14 air conditioning, with properly oriented
Figure 5: Average SMUD PV Customer Load vs. Net Load
28 reFOCUS
July/August 2005
Notes
solar systems in a ZEH has the potential of even larger peak demand reduction in new homes. Monitored energy use and solarproduction data from a Lakeside ZEH model home shows potential peak demand reduction of up to of 2.6 kW per home. In 2004, more than 9,000 new homes were built in SMUD's service territory. If these homes had been built to the ZEH standard, including a package of high efficiency measures designed to reduce air conditioning (peak) electrical consumption and a 2 kW AC PV system, the District could have realized a significant peak load reduction - up to 20 MW, especially if the PV systems had been oriented west of south. It is too soon to draw conclusions regarding what long-term impacts the Premier
1. SMUD set a new system peak electric demand in 2003 of 2,809 MW on July 23, 2003. 2. A western oriented solar system can produce up to 43% more power during the District's peak period versus a true south-oriented solar system. 3. The Lakeside ZEH model home is a 2,300 square foot, one-story home and was operated as a showroom, not a typical home, suggesting further savings. For example, the thermostat was set at 72° F or lower, all lights, ceiling fans (the home had 5 ceiling fans) and a large video monitor was continuously operating. All these additional loads, especially the lights, add heat loads to the model home, which are not typical of a normal home.
Figure 6: Average New Home Load vs. PV Production 22 July 03
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SETTING A NEW STANDARD Zero Energy Homes in the US The United States is undergoing an unprecedented boom in new air conditioning is a standard feature in all home construction. California and its capital Sacramento have new homes built in Sacramento and a major factor in SMUD's peak electrical demand been a part of that boom with record numbers of new homes growth. SMUD is participating in the ZEH built in the last few years. This boom in new home construction initiative because the District believes ZEH is leading to increased demand for electricity, raising utility bills can reduce its peak demand while dramatiand taxing local electrical utility systems. Solar PV is playing a cally reducing new homeowners' utility bills. major role in meeting electricity demand in the region. Mike Keesee, Sacramento Municipal Utility District reports. The SMUD Zero Energy
Home
O
ne of the major appeals of photovoltaic energy is its ability to transform new homes into miniature power plants. Installing a solar electric system on a new home with advanced energyefficiency features creates the potential of home that generates nearly as much electricity as it consumes on an annual basis. This is the promise of a "Zero Energy Home (ZEH)." Since 2003, the Sacramento Municipal Utility District (SMUD), which is the customer-owned electricity provider in
Sacramento, has been working with the U.S. Department of Energy's (DOE) Building American program to encourage local production home builders to build (and sell) ZEHs. DOE's ZEH initiative combines state-of-the art, energy-efficient construction and appliances with commercially available renewable energy systems such as solar electricity. DOE's goal is to help builders create homes that produce as much energy as they use over the course of a year and reduce a new home's total energy bill, electric and gas, by at least 60%. Central
SMUD leads a collaborative effort between the US DOE, the National Renewable Energy Laboratory (NREL), ConSol (DOE's ZEH consultant) and major PV manufacturers, including GE Energy and BP Solar, in working with local new homebuilders to build the ZEHs in the region, including the first all ZEH community at Premier Gardens. The first step in designing a ZEH is to dramatically reduce a home's overall energy use. This enables the homebuilder to install a smaller photovoltaic system to meet the home's electrical needs and, more importantly, helps to reduce the ZEH's overall costs. ConSol put together a package of energy efficiency measures that helped reduce the ZEH's heating and water heating energy use by over 15% and cooling energy use by 50% compared to California's stringent Title-24 building energy standards. A typical ZEH built in Sacramento About the author Mike Keesee is the project manager for the Sacramento Municipal Utility District's (SMUD)'s Zero Energy Home program. He has also managed the SMUD Advantage Home program, the utility's Residential New Construction program. www.smud.org
Figure 1: Premier Gardens Zero Energy Home
26 reFOCUS
July/August 2005
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.
BIPV
Figure 2: GE PV-055 Module (Courtesy of GE Energy)
(Figure 1) includes the following energy efficiency measures: • • • • • •
Low air infiltration Vinyl, low-e, spectrally selective windows 92 percent efficient furnace (AFUE .92) SEER 14 with TXV air conditioner Engineered heating and cooling duct runs Tankless, instantaneous water heater with a .82 Energy Factor • Insulated Hot Water Pipes • Fluorescent Lighting • Third-Party inspection and testing of the home's energy efficiency features, such as the quality of the insulation installation, (qualifying the home as an Energy Star Home). One of the major goals of SMUD's ZEH program is to encourage local homebuilders to adopt newly introduced Roof-Integrated PV (RIPV) products. The first ZEH homes utilized a 2.0 kW AC RIPV system manufactured by GE Energy. The GE Energy solar electric system consists of 48 PV-055 modules (Figure 2) and a SMA "Sunnyboy" 2500 inverter. The system also features a unique "PV" meter supplied by SMUD to record the energy output of the solar system, which is recorded on the homeowner's monthly electric bill. As part of the ZEH research efforts, SMUD is also evaluating the performance of new RIPV products. Of particular concern is whether high roof temperatures will affect RIPV products' performance. SMUD operates its own PV Performance Index. SMUD's PV Performance Index is a software tool developed for evaluating PV system performance based on local, real-time weather data. Weather data is collected from local weather stations and used to estimate PV production based on individual PV system characteristics. This baseline PV Production number is then compared to actual monthly PV system production meter reads. To date,
www.re-focus.net
the GE Energy RIPV system is performing exceptionally well, consistently exceeding 100% of expected kWh production.
ZEH program experience Since 2003, 107 ZEHs have been built in the SMUD service territory. Morrison Homes introduced the first ZEH in Sacramento in 2003 at its Lakeside project where ZEH was offered as an optional upgrade to homebuyers. In 2004, Premier Homes became the first new homebuilder in Sacramento to construct an entire ZEH community called, Premier Gardens. Premier Gardens is a 95unit, "in-fill" project designed for first-time homebuyers. "In-fill" developments are those built inside areas where there already is existing development, rather than in outlying, suburban or "exurban" areas. In-fill developments offer a unique opportunity for middle class families to be closer to work and minimize their commute time. In 2005, a 32unit ZEH project will be built by Treasure Homes (Figure 3).
Energy use and electric bill impacts The Premier Gardens ZEH project offers an unprecedented opportunity for SMUD to compare the impact that ZEH features have on customer's energy use and bills. Adjacent to the Premier Gardens project, a competing homebuilder built 95 similarly sized homes marketed to the same demographic. As a result, the Premier Gardens ZEH energy use, electric peak demand, and utility bills can be compared to the energy use, electric peak demand, and bills of SMUD customers living in the adjoining non-ZEH homes. Data collected for the first ten months of occupancy indicate that residences living in ZEHs use less electricity and have lower electricity bills than those living in homes with enhanced energy efficiency measures only. On average, Premier Gardens
homeowners used 16 percent less electricity than those living in the non-ZEH homes: 5,260 kWh versus 6,252 kWh (Figure 4). The PV systems in the Premier Garden ZEHs are supplying more than 47 percent of the electricity used in the home, 2,498 kWh of the total 5,260 kWh consumed. Over the same 10-month period Premier Gardens homeowners average monthly electric bills were 54 percent lower than the Cresleigh homeowners, $30.48 versus $65.80 and 58% lower than the average monthly SMUD Residential gas-heated customer bill, $73.06 versus $25.89. A closer look at the individual customers' April bills shows the impact a ZEH has on reducing a customer's electric bill. For this period, the ZEHs' average electric bill was 78% lower than the typical SMUD bill and 63% lower than the neighbouring homes right across the street.
Peak demand impact More than 70 percent of SMUD's electric demand growth is driven by new homes (40 MW of the 56 MW of peak load growth in 2003 compared to 2002). The District's system load profile nearly matches the average new home's load profile on the system's peak day (July 22, 2003), confirming the contribution of new homes' load to setting coincident peak electrical demand. Data collected from a sample of 30 SMUD customers participating in the PV Pioneer retrofit and Solar Advantage Home PV programs indicate that PV systems can reduce a home's peak electrical demand by as much as 13 percent (0.4 kW). Figure 5 shows the impact that a PV system has on a
Figure 3: Premier Gardens ZEH Community 95 Zero Energy Homes with 2 kW Solar Systems
July/August 2005
reFOCUS 27
BIPV
Garden ZEH homes will have on customer electrical usage, bills, and peak demand, or the District's electric system. SMUD will conduct whole house monitoring of the ZEH homes in Premier Gardens and the adjacent subdivision for two years. Electrical usage, bills, and peak demand data will be gathered from eighteen homes from each housing development and compared. In addition, solar system performance will be tracked in the Premier ZEHs and correlated with the homes' peak demand to determine the impact ZEH solar systems have on the District's system peak. As data are collected from these homes, a clearer picture of the impact ZEHs have on electrical consumption and peak demand will be reported. Figure 4: ZEH Monthly Average kWh Usage Premier vs. Cresleigh
customer's net electrical demand in July. The top line represents the hourly electric load for a PV customer. The bottom line shows the PV customer's net load, or the amount of electricity supplied by SMUD. The difference between the two lines is made up by the customer's PV system generation. Similarly, comparing an average new home's load to its PV output illustrates the potential for reducing a new home's peak demand. Figure 6 shows the impact a southwestern-oriented 2 kW AC PV system would have on reducing the average new home's peak demand. In this example, the home's peak demand which occurred at 6 p.m. is reduced by 20 percent (0.9 kW). Combining high efficiency measures, such as SEER 14 air conditioning, with properly oriented
Figure 5: Average SMUD PV Customer Load vs. Net Load
28 reFOCUS
July/August 2005
Notes
solar systems in a ZEH has the potential of even larger peak demand reduction in new homes. Monitored energy use and solarproduction data from a Lakeside ZEH model home shows potential peak demand reduction of up to of 2.6 kW per home. In 2004, more than 9,000 new homes were built in SMUD's service territory. If these homes had been built to the ZEH standard, including a package of high efficiency measures designed to reduce air conditioning (peak) electrical consumption and a 2 kW AC PV system, the District could have realized a significant peak load reduction - up to 20 MW, especially if the PV systems had been oriented west of south. It is too soon to draw conclusions regarding what long-term impacts the Premier
1. SMUD set a new system peak electric demand in 2003 of 2,809 MW on July 23, 2003. 2. A western oriented solar system can produce up to 43% more power during the District's peak period versus a true south-oriented solar system. 3. The Lakeside ZEH model home is a 2,300 square foot, one-story home and was operated as a showroom, not a typical home, suggesting further savings. For example, the thermostat was set at 72° F or lower, all lights, ceiling fans (the home had 5 ceiling fans) and a large video monitor was continuously operating. All these additional loads, especially the lights, add heat loads to the model home, which are not typical of a normal home.
Figure 6: Average New Home Load vs. PV Production 22 July 03
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