The rapidly growing world energy use has already raised concerns over supply difficulties, exhaustion of energy resources and heavy environmental impacts (ozone layer depletion, global warming, climate change, etc.). The global contribution from buildings towards energy consumption , both residential and commercial, has steadily increased reaching figures between 20% to 40% in developed countries, and has exceeded the other major sectors: industrial and transportation.
Energy consumption in the world arose by 5% in 2010. This happened after the slightly decrease in 2009. In 2009, world energy consumption decreased for the first time in 30 years (-1.1%), as a result of the financial and economic crisis (GDP drop by 0.6% in 2009). This influential increase is the result of two converging conditions. In one condition, industrialized countries, which experiences sharp decreases in energy demand in 2009 and recovered in 2010, are coming back to historical trends. Oil, gas, coal and electricity markets followed the same trends. On the other hand, some countries like China and India, not slowing down in 2009, continued their intense demand for all forms of energy. The data used for the calculation of the energy efficiency indicators were taken from ENERDATA world energy database.
Buildings represents nearly 40% of global energy consumption. And this can rise up to 50% if the energy spent to manufacture the materials and equipment used in them is included. Nearly 40% of U.S primary energy is consumed in building sector. The industrial sector was responsible for 32% and transportation sector 28% of total. Of the 40 quads consumed in the buildings sector, homes accounted for 54% and commercial buildings accounted for 46%. As for energy sources, 76% came from fossil fuels, 15% from nuclear generation, and 8% from renewable.The buildings sector consumed 20 quads of delivered (site) energy in 2010. Delivered energy does not include energy lost during production, transmission, or distribution to customers. The top four end uses—space heating, space cooling, water heating, and lighting—accounted for close to 70% of site energy consumption. Other end uses, consumer electronics, kitchen appliances, and ventilation made up the remainder.
Buildings represents nearly 40% of global energy consumption. And this can rise up to 50% if the energy spent to manufacture the materials and equipment used in them is included. Nearly 40% of U.S primary energy is consumed in building sector. The industrial sector was responsible for 32% and transportation sector 28% of total. Of the 40 quads consumed in the buildings sector, homes accounted for 54% and commercial buildings accounted for 46%. As for energy sources, 76% came from fossil fuels, 15% from nuclear generation, and 8% from renewable.The buildings sector consumed 20 quads of delivered (site) energy in 2010. Delivered energy does not include energy lost during production, transmission, or distribution to customers. The top four end uses—space heating, space cooling, water heating, and lighting—accounted for close to 70% of site energy consumption. Other end uses, consumer electronics, kitchen appliances, and ventilation made up the remainder.
BUILDING SECTOR IN INDIA
With consistent rise of 8% annual energy consumption in residential and commercial sector, building energy consumption has been increase from a low 14% in the early 1970s to nearly 33% (Climate Works, 2010). The gross total built-up area added to commercial and residential space was about 40.8 million square meter in 2004-2005, which is about 1% of annual average constructed floor area around the world, and tends to show a sustained growth of 10% over coming years.
With consistent rise of 8% annual energy consumption in residential and commercial sector, building energy consumption has been increase from a low 14% in the early 1970s to nearly 33% (Climate Works, 2010). The gross total built-up area added to commercial and residential space was about 40.8 million square meter in 2004-2005, which is about 1% of annual average constructed floor area around the world, and tends to show a sustained growth of 10% over coming years.
Energy consumption in buildings can be bench marked in a variety of ways - Primary (source) Energy consumption, Secondary (site) Energy consumption, Final (metered) Energy consumption and Carbon Emission. Primary energy is the energy in the fuel source, such as coal, oil or natural gas, before they are converted to Secondary source of energy such as electricity used in buildings. The energy consumption reading at the meter is the final. The four common units for energy consumption are kWh (Kilowatt hours), Mj (Mega Joules), Btu (British thermal unit) and toe (Tons of oil).
In buildings, the use of metered energy consumption (kWh) as an energy benchmark rather than primary energy or CO2e can be misleading when the fuel source or grade of energy (heat or electricity) varies. To understand this better, consider which system has the lowest energy consumption to heat a room in a house – an electric convector heater, central gas heating system or electric heat pump. If a space requires 2,000 Watts of heat for 5 hours this is a heat energy requirement of 10 kWhheat. In a simple convector heater an electric current is passed through a wire providing an electrical resistance. This resistance converts the energy in the electric current into heat with an efficiency close to 100%. In a new central heating system the efficiency of converting natural gas into heat energy is approximately 90%. The efficiency with which a heat pump converts electricity into heat is called the Coefficient of Performance (CoP):
CoP = Heat energy output / Electrical energy input
A heat pump with a CoP of 2.7 converts 1 kWh of electricity into 2.7 kWhheat by extracting (or pumping) heat energy from an external source such as the air or ground.
CoP = Heat energy output / Electrical energy input
A heat pump with a CoP of 2.7 converts 1 kWh of electricity into 2.7 kWhheat by extracting (or pumping) heat energy from an external source such as the air or ground.
It is interesting to observe that the Meter (Final) Energy consumption of Electric Convector is less than that of Gas Boiler, however its Primary (source) energy Consumption is much higher. Similarly, the Meter (Final) Energy Consumption of Gas Boiler is much higher than Electric Heat Pump, yet they both have similar Carbon Emission rate. The carbon intensity of grid electricity also varies from 0.1 kgCO2e/kWh in Brazil due to extensive use of nuclear plants to 1.42 kgCO2e/kWh in India due to coal power station and high distribution losses. Here low carbon electricity doesn't mean it has minimal effect on environment. Countries like France with Low carbon nuclear power generated electricity are struggling with Nuclear waste. On other side, countries like Australia with high carbon intensity of electric grid has led to use of gas CHP in buildings to reduce CO2 emissions to obtain better energy, but this doesn't lead to reduction in use of energy. Hence, there is no perfect unit or method to benchmark energy and carbon performance of building internationally.
References:
1. Enerdata - Global Energy Intelligence
2. Building Energy Data Book - U.S Department of Energy
3. What color is your Building
2. Building Energy Data Book - U.S Department of Energy
3. What color is your Building