Table 41 Alternatives to Fossil Fuels for Heating and Cooling

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Where Available or Possible

Absorption cooling


Combined heat and power (cogeneration)

Concentrating solar thermal

District heating (or cooling)

Geothermal high-temperature heat

Ground-source heat pump

Passive solar heating Passive cooling

Seawater or lake cooling

Solar thermal heat system

Uses a heat source (such as the sun or waste heat from combined heat and power (CHP)) to cool air through an evaporative process; small to large-scale

Heat derived from the combustion of biomass, such as wood or pellets; residential to large-scale

Use of a power plant to produce both heat and electricity; residential to large-scale

Uses optical concentrators to focus the sun to provide higher-temperature heat and steam for industrial processes (and thermal electricity production)

Distribution of heating (cooling) from a central generating site, through a piped network, to meet local residential and commercial needs

Geothermal steam or hot water used for district water and space heating, warming greenhouses,aquaculture, spas and swimming pools, industrial purposes (and thermal electricity production)

Pump that makes use of ground-stored solar heat or well water to provide space and water heating/cooling; residential to large-scale

Collects solar heat through appropriate building orientation and window placement

Avoids excess heat absorption by designing buildings to reduce passive solar gain, such as avoiding glass and using passive ventilation

Harnesses constant coolness of deep water to provide space cooling (and cold water) to buildings through a piped network

Uses the sun's heat to provide space and water heating for buildings and low-temperature heat and hot water for industrial processes


Anywhere close to sustainable wood or other biomass resources


Needs clear skies as in Spain, North Africa, parts of China and India, or U.S. Southwest

Possible anywhere for use in urban and campus settings with multiple buildings

Regions of active or geologically young volcanoes, including Iceland, western North and South America, Philippines, Japan, East Africa


Anywhere heating is needed Hot, particularly dry, regions

Requires proximity to cold water resource (along deep rivers, lakes, or coastlines)

Anywhere fossil fuels to biomass for district heating, reducing associated emissions to less than one third their 1980 level. Austria and Den mark also rely heavily on biomass to heat homes, farms, and district systems. Poland is replacing coal with biomass for power and

An End urin g En ergy Future heating needs. Biomass can directly replace fossil fuels, and modern wood burners can convert biomass to heat at efficiency rates of up to 90 percent.39

Geothermal energy is used for everything from space heating and cooling to warming greenhouses and melting snow on roads and bridges. In France, Iceland, New Zealand, the Philippines, Turkey, the United States, and other countries with high-temperature resources, geothermal heat is used for electricity generation, district heat, and industrial processes like pulp and paper production. Ground-source heat pumps, which can be used virtually anywhere, use the stored solar energy of Earth or well water as a heat sink in summer and heat source in winter. The United States has the world's largest heat pump market, with up to 60,000 systems installed annually.40

Because buildings generally require heat as well as electricity, combined heat and power units can be designed to supply both. CHP plants generate electricity and capture remaining heat energy for use in industries, cities, or individual buildings. They convert about 75-80 percent of fuel into useful energy, with efficiencies exceeding 90 percent for the most advanced plants. As a result, even traditional fossil fuel CHP systems can reduce carbon emissions by at least 45 percent. These systems can also make use of absorption chillers for space cooling to lower electricity demand even further. Residential-scale CHP units have been widely available in Japan and Europe for years and were recently introduced in the United States.41

Seawater and lake source district cooling systems have been developed for a range of climates, from Kona in Hawaii to Stockholm in Sweden, and can save more than 85 percent of the energy required for conventional air conditioning. The cold waters of

Lake Ontario provide district cooling to Toronto in Canada; the system has the capacity to cool more than 3.2 million square meters of building space, avoiding 79,000 tons of CO2 annually. Many of the world's big cities are near large water bodies, which they could tap for cooling. And as paradoxical as it might seem, solar energy can also provide cooling via the oldest form of air conditioning technology—absorption cool-ing—with the same devices that provide heat in the winter. While such systems are still relatively costly, several are already in operation, including a solar-driven cooling system in Phitsanulok, Thailand.42

Economical heat storage over a wide range of temperatures and time periods can significantly increase the potential of renewable systems. Some storage options are already available and cost-effective, particularly in combination with large-scale district systems. For example, surplus solar heat in summer can be transferred to underground storage for space and water heating in winter.43

According to the IEA, "solar water heating, biomass for industrial and domestic heating, deep geothermal heat and shallow geothermal heat pumps are amongst the lowest cost options for reducing both CO2 emissions and fossil fuel dependency. In many circumstances these technologies offer net savings as compared to conventional heating systems in terms of life-cycle costs." And yet these renewable sources and technologies currently meet only 2-3 percent of total demand.44

Attitudes have begun to change as fuel prices rise and countries recognize the enormous potential of renewables. To date, the most successful countries have enacted combinations of policies to address the different barriers facing renewable heating and cooling technologies. These include lack of public awareness, the need to train a work force and educate city planners and architects about

An Enduring Energy Future integrating renewables, high upfront costs, the "tenant-owner" dilemma (where building owners and inhabitants are different people, and the person who pays does not benefit), and the need for scale.45

Cloudy Germany has one of the largest solar thermal heat markets in the world thanks to public awareness of the technology and long-term government investment subsidies. The German state of Baden Württemberg now requires that all building plans for new homes include renewable systems to meet at least 20 percent of space and water heating needs, and as of 1 January 2009 the German federal government requires new buildings to meet at least 15 percent of their heating requirements with renewable sources. Since 2006 Spain has mandated solar systems for all new or renovated buildings, and Hawaii will require solar water heaters on all new homes starting in 2010.46

DLR in Germany projects that 12 of the 20 largest economies could meet at least 40 percent of their heating needs with renewables by 2030, representing a significant increase from current shares for most countries. (See Figure 4-3.) By 2050, renewables' share in the majority of these countries could exceed 60 percent, according to DLR and REN21 estimates, with renewables supplying at least 70 percent of heating in some countries.47

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