Heating in Buildings

The second axis of energy efficiency improvement is the heating of space and water in a building. Here, there are significant differences between OECD countries and other regions. In new economies, biomass (waste, wood) remains the primary source of heating, accounting for around 70% of total heating in India and 50% in China, against less than 10% in Europe. In OECD countries, boilers are the main source of heating. The energy efficiency yield of traditional boilers is poor, around 70%. Electrical heating is much better, with a yield of 100%, but this needs to be balanced as electricity production is extremely inefficient, with yields around 3040%. Boiler technologies have improved over the last years, and new condensation boilers can reach up to 95% yield. Going further, heat pumps have excellent yields of above 100% (which means the energy delivered is above the one necessary to its operation). Hybrid heat pumps combine several heating sources to limit the amount of energy necessary to deliver the desired temperature gradient. Hybrid pumps can for instance be coupled to renewable energy such as a solar or a geothermal energy source. The heating of water is also a significant area of energy consumption in a building, in particular in the residential segment. Traditional water boilers are inefficient from an energy standpoint as they provide hot water at any time of the day. Hot water storage can lead to energy inefficiencies of 10-30%, depending on the geographical region. The efficiency of water boilers can first be greatly improved by not storing hot water. Instant heating technologies significantly reduce the energy necessary for heating. Japanese industry has created a boiler which is powered by a heat pump. Half a million of such boilers are manufactured every year, but only in Japan. Heating can also be thought out more globally, beyond the efficiency of the equipment used. The typical yield of a thermal power plant is around 30-40%. The rest of the energy is generally lost as heat. Cogeneration reuses this heat and distributes it through a heating network. Consequently the yield of cogeneration plants goes up to 80 or 90% in the best cases. The main issue here is the deployment of cogeneration technology. Heating infrastructure need to be built or upgraded for this use. Furthermore, cogeneration plants need to operate at a specific nominal rate, or their efficiency decreases rapidly. The quantity of both electricity and heat also needs to be calculated precisely. Cogeneration is mainly used in North Europe; 40% of the electricity production in Denmark is done using cogeneration power plants.

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