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Hot water
Green Heat
Hot water Continuing his regular column, Bill Eggertson reminds us of the great underused global potential that still exists for using green heat technologies to heat water.
M
ention the word 'heating' and most people (certainly those of us who live in northern climates) likely will think of the need to keep ourselves warm during the winter by turning up the thermostat of an oil or gas-fired furnace, electric baseboard heaters or, at best, an advanced biomass combustion chamber (more commonly called a wood stove). Mention the term 'Green Heat' and then add a little bit of explanation, and most people will grasp the concept that heating a room to 20oC requires low-grade thermal energy which can (and should) be achieved with a ground-coupled earth energy heat pump or with solar thermal water (or air) collectors, or with that wood stove. These four Green Heat technologies emit lower GHG emissions than conventional space heating options, and can supply the desired thermal target at much lower operating cost. But green heating is much more than just warming a house. If its scope were that limited, there would be little need for Green Heat technologies to be considered in warmer climes around the world. As we noted in our last column, space cooling is a major application for secondary energy in many regions, and it places an increasing demand on electric utilities to diffuse their peak demand to reduce the load for air conditioning. One increasingly popular option is to increase the installed capacity of green cooling technologies (those Green Heat technologies which can also provide space cooling) as a means of obtaining the economic and environmental benefits of low-grade thermal energy from renewables. To advance my argument, allow me to quote from government data on secondary energy use in Canada (my home base). Between 1990 and 2003, total secondary energy use in the residential sector
56 reFOCUS
September/October 2005
rose 13%, with space heating rising 11% (partly thanks to higher levels of energy efficiency and conservation in the building envelope) while consumption for appliances (mainly electric-powered) rose 7%. However, during that period, energy consumption for space cooling rose 113%. It should also be noted that total residential floorspace across Canada rose 29% during that time, and the number of homes increased by 23% while energy intensity dropped 13% per square metre (and declined 8% per household). Heating degree-days rose 5%, but cooling degreedays rose 23%. In the commercial/institutional sector, total national floorspace increased 24% over the 13 years, and secondary energy consumption in this sector rose 36%, with space heating jumping 43% and energy for auxiliary equipment, motors and lighting rising 17%. The major increase in energy consumption? You guessed it: demand for space cooling rose 93%. Which brings us to the third leg of the Green Heat paradigm: water heating. This is a significant energy demand that often is over-looked by consumers because the application frequently uses the same heating unit that warms the space, or the monthly cost is paid as part of the invoice for natural gas or electricity, thereby reducing its visibility. However, while space heating is needed in winter and space cooling is needed in summer, water heating is needed in all 12 months. In Canada, approximately 20% of a home's total annual energy demand is for heating water while, in warmer regions (where the large amount of space heating is removed), the ratio between water heating and space cooling becomes even more dramatic. Expanding on the Canadian data noted above, residential energy consumption for water heating rose 15% over the 13-year period, but demand for that application jumped 49% in the commercial /
institutional sector. The relative share of water heating demand will continue to rise as cold-climate countries increase the required level of insulation to stem the demand for space heating, and as appliance efficiency increases to reduce the number of electrons needed to power lights, refrigerators and other plug load. Since most developed nations use natural gas or electricity to heat water, the need to meet that demand from Green Heat technologies becomes even more relevant. (This entire argument temporarily ignores the significant consumption in developing nations of biomass for warming water needed for cooking, which frequently is the only application for energy in these regions.) In the industrial sector, green heating and green cooling have less relevance for space conditioning for a number of reasons, but the supply of hot water in this sector can often be significant, with widespread use in car washes and laundromats, as well as crop drying and road deicing, among others. Depending on conventional fuels, these technologies can cost-effectively pre-heat water for a range of industrial processes, thereby reducing the price of conventional fuels to boost that final water temperature. This column is dedicated to advocating the logic that low-grade thermal energy demand should never be met from the consumption of high-grade energy (such as electricity, even if it is from wind turbines) in any situation where the economic and environmental benefits of Green Heat technologies are so overwhelming. Save the perfect sine waves for computers and sensitive electronic equipment; reduce grid congestion and ancillary problems by developing the practicality of decentralized energy sources and distributed resources. Water heating is another application where Green Heat can be a global solution, and it will become an increasingly important and relevant solution as rigorous attention is given to the other applications which spring so readily to mind. [email protected]
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.
Hot water Continuing his regular column, Bill Eggertson reminds us of the great underused global potential that still exists for using green heat technologies to heat water.
M
ention the word 'heating' and most people (certainly those of us who live in northern climates) likely will think of the need to keep ourselves warm during the winter by turning up the thermostat of an oil or gas-fired furnace, electric baseboard heaters or, at best, an advanced biomass combustion chamber (more commonly called a wood stove). Mention the term 'Green Heat' and then add a little bit of explanation, and most people will grasp the concept that heating a room to 20oC requires low-grade thermal energy which can (and should) be achieved with a ground-coupled earth energy heat pump or with solar thermal water (or air) collectors, or with that wood stove. These four Green Heat technologies emit lower GHG emissions than conventional space heating options, and can supply the desired thermal target at much lower operating cost. But green heating is much more than just warming a house. If its scope were that limited, there would be little need for Green Heat technologies to be considered in warmer climes around the world. As we noted in our last column, space cooling is a major application for secondary energy in many regions, and it places an increasing demand on electric utilities to diffuse their peak demand to reduce the load for air conditioning. One increasingly popular option is to increase the installed capacity of green cooling technologies (those Green Heat technologies which can also provide space cooling) as a means of obtaining the economic and environmental benefits of low-grade thermal energy from renewables. To advance my argument, allow me to quote from government data on secondary energy use in Canada (my home base). Between 1990 and 2003, total secondary energy use in the residential sector
56 reFOCUS
September/October 2005
rose 13%, with space heating rising 11% (partly thanks to higher levels of energy efficiency and conservation in the building envelope) while consumption for appliances (mainly electric-powered) rose 7%. However, during that period, energy consumption for space cooling rose 113%. It should also be noted that total residential floorspace across Canada rose 29% during that time, and the number of homes increased by 23% while energy intensity dropped 13% per square metre (and declined 8% per household). Heating degree-days rose 5%, but cooling degreedays rose 23%. In the commercial/institutional sector, total national floorspace increased 24% over the 13 years, and secondary energy consumption in this sector rose 36%, with space heating jumping 43% and energy for auxiliary equipment, motors and lighting rising 17%. The major increase in energy consumption? You guessed it: demand for space cooling rose 93%. Which brings us to the third leg of the Green Heat paradigm: water heating. This is a significant energy demand that often is over-looked by consumers because the application frequently uses the same heating unit that warms the space, or the monthly cost is paid as part of the invoice for natural gas or electricity, thereby reducing its visibility. However, while space heating is needed in winter and space cooling is needed in summer, water heating is needed in all 12 months. In Canada, approximately 20% of a home's total annual energy demand is for heating water while, in warmer regions (where the large amount of space heating is removed), the ratio between water heating and space cooling becomes even more dramatic. Expanding on the Canadian data noted above, residential energy consumption for water heating rose 15% over the 13-year period, but demand for that application jumped 49% in the commercial /
institutional sector. The relative share of water heating demand will continue to rise as cold-climate countries increase the required level of insulation to stem the demand for space heating, and as appliance efficiency increases to reduce the number of electrons needed to power lights, refrigerators and other plug load. Since most developed nations use natural gas or electricity to heat water, the need to meet that demand from Green Heat technologies becomes even more relevant. (This entire argument temporarily ignores the significant consumption in developing nations of biomass for warming water needed for cooking, which frequently is the only application for energy in these regions.) In the industrial sector, green heating and green cooling have less relevance for space conditioning for a number of reasons, but the supply of hot water in this sector can often be significant, with widespread use in car washes and laundromats, as well as crop drying and road deicing, among others. Depending on conventional fuels, these technologies can cost-effectively pre-heat water for a range of industrial processes, thereby reducing the price of conventional fuels to boost that final water temperature. This column is dedicated to advocating the logic that low-grade thermal energy demand should never be met from the consumption of high-grade energy (such as electricity, even if it is from wind turbines) in any situation where the economic and environmental benefits of Green Heat technologies are so overwhelming. Save the perfect sine waves for computers and sensitive electronic equipment; reduce grid congestion and ancillary problems by developing the practicality of decentralized energy sources and distributed resources. Water heating is another application where Green Heat can be a global solution, and it will become an increasingly important and relevant solution as rigorous attention is given to the other applications which spring so readily to mind. [email protected]
1471 0846/05 © 2005 Elsevier Ltd. All rights reserved.