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Solar hot water systems provide domestic hot water and also contribute to space heating using solar energy. The efficiency of rooftop solar water heaters depends on the type of collector and storage tank among other parameters. Evacuated tube collectors are among the efficient type of solar collectors available capable of delivering hot water temperatures upto 180 °C. IEA Blue Map scenario envisions a reduction of global energy related CO2 emissions by half to their 2005 levels by 2050. According to the scenario the use of solar water heaters for hot water in buildings will grow providing for 30 per cent to 60 per cent of water heating demand today. This scenario assumes that heat pumps will be increasingly deployed for space and water heating and they will account for 63 per cent of the heating and cooling technology energy savings in 2050 (IEA, 2007). Transformation of heating and cooling technology market according the IEA Blue Map Scenario will reduce 2Gt of CO2 emissions globally. According to data from the energy saving trust, UK typical carbon savings in the UK because of solar hot water heaters are around 230kgCO2/year when replacing gas and 510kgCO2/year when replacing electric immersion heating.
Total solar thermal capacity installed worldwide by the end of 2011 reached 234.6 GWth. In terms of solar thermal installed capacity China is by far the leader, due to low costs and government support. The EU-27 is the second largest market, with the majority of installations located in the South. When evaluating the SWH market on per capita basis the ranking changes completely. Small sunny countries like Cyprus and Israel dominate the scene (see market scenario below). Relatively higher rankings for Austria, Germany and Denmark prove that the availability of solar resources is not the only the im-portant factor, supportive policies to encourage deployment need also to be in place (Mauthner and Weiss, 2013).
Globally all three types of collectors are used for harnessing solar energy for water heating i.e., evacuated tube, flat-plate, and ICS systems. In China solar installed capacities are mainly for evacuated tubes, while in Turkey, Germany, Japan and Israel etc., mainly glazed flat plate collectors are installed. In the US, unglazed plastic flat plate collectors for swimming pools account for most installed capacity (see graphics below).
Warm and tropical countries have great potential for renewable energy based end-use water heating systems (i.e., Solar Water Heaters) because of the suitable climatic conditions. South Africa is one of these countries that have recognized this potential. The country had a total installed SWH capacity of 173 MWth in 2009. In 2010 the government launched a program to substantially reduce the costs of SWHs and accelerate mass rollout of at least 1 million units by 2014. 70 per cent of the 1 million target of SWHs installation focuses high-income households at R 15,000 (Euro 1,387) a unit and 30 per cent in low-income households at R 8000 (Euro 739) a unit. A government funding of R12.9 billion (Euro 1.2 billion) was required to provide subsidies on the installed costs of SWHs. Given the funding of this magnitude was not possible via the fiscus, a demand side initiative was thought to be the most feasible alternative. The electricity company Eskom that generates 95 per cent of electricity demand in South Africa was asked to collect funds through increased electricity tariffs. The amount to be built into the tariff would be based on a similar principle to that applied in setting the Renewable Energy Feed-In Tariffs. Every kilowatt-hour of energy saved through SWH installation attracts a certain incentive that is build into the tariff. Projections suggest that the installation of only 1 million SWHs will reduce demand for coal-based electricity by 620 MW and avoid 1,491,000 tons of CO2 emissions creating a positive impact on the environment in the country (Eskom.co.za, 2016; Bigee.net, 2016).
Some countries in the Middle East are progressively benefitting from solar irradiation and have high rate of SWH installation capacity, for example Israel. Use of solar water heating in Israel dates back to 1950s when a fuel shortage caused the government to enact a hot water ban. Solar water heating was developed in response and, by 1967, 1/20 households used a solar water heater. After the energy crisis in the 1970s, in 1980 legislation came into effect that required the installation of water heaters in all new constructions up to 27 m. Now, more than 80 per cent of the households in Israel obtain their domestic hot water from solar rooftop heaters. A typical domestic unit consists of a 150 litre insulated storage tank and 2 m2 of collector area (Mauthner & Weiss, 2012).
According to a survey by the Globescan in 2009, 38 per cent of Indian residences have the feature of hot running water. Electric instantaneous water heaters provide hot water in 45 per cent of the residences followed by gas instantaneous in 20 per cent and solar water heaters in 15 per cent (National Geographic/Globescan 2012). In terms of Solar Water Heater Systems SWHSs installation India currently ranks fifth and accounts for an installed capacity of 1.4 per cent of the total heating capacity through solar water heaters around the world. Up until the end of October 2009, 3.12 million m2 of solar water heating collector area was achieved (MNRE & REEP, 2010). The first serious effort to disseminate the technology started with the formation of the Department of Non- Conventional Energy Sources (DNES) in 1982. However, a number of events acted in favour of the up-take of solar water heaters including the continuing increases in electricity tariffs as well as problems associated with the electricity supply such as outages and voltage fluctuations. Most parts of India receive high amount of solar radiation, in winter (September to January) for example, solar insolation in western Rajasthan, Jammu & Kashmir and lower western coast ranges between 2.3 and 5.9 kWh/m2/day. This makes solar water heating an attractive and viable option. The potential global solar water heating installed capacity is forecast to reach 9,75GWth by 2030, with China still holding 50 per cent of the potential, followed by India with 10 per cent (Bloomberg, 2011).
In Brazil, Columbia, Ecuador and Guatemala, electric water heaters account for 20 to 25 per cent of residential electricity demand. In Brazil instant (rather than storage) electric water heaters are widely used for showers. Brazil accounts for the sale of 62 per cent of world market for instantaneous water heater for the shower (Bosch, 2012). There is a great potential for replacing the fossil fuse fired electric water heaters with SWHs. Solar water heating installed capacity in Brazil is growing but the growth to create market transformations is modest considering the country’s solar potential. The SWH sector has been growing steadily since the Brazilian energy crisis in 2001. However, the growth is modest to create market transformations given the country solar capacity at the end of 2011 survey among the SWH manufacturers the national average of installed solar collector area was only 18.4 kWth/1,000 inhabitants (Mauthner and Weiss, 2013). The county plans to construct about 1 million new houses for low income population over the coming years, which provides an opportunity to be creative with incentives in order to accelerate the SWH market.
Barbados has been the undisputed leader in solar hot water systems regionally for over 30 years. In 2008 the country accounted for 75 per cent of the SWHs used in the Caribbean and the country currently manufactures more than 80 per cent of the SWH demand in the region. The main reason that the SWHs saw a greater up-take in Barbados and not in the other Caribbean Islands is because of the tax incentives provided by the Barbados government. However, the SWH industry in all islands will soon be taking off as a result of opportunities of mass production of systems from Asia (Escalaante, 2006).
According to building standards in the EU average consumption of hot water per person is around 30 litres per day. This average applies Monday-Sunday with Sunday usage being on average considerably higher (Kemna et al., 2007). Water heating in 19 member countries of International Energy Agency (IEA) countries accounted for 16 per cent of final household energy consumption in 2006 (Reece 2011). The 191.4 million households in the EU25 consume per household an average of 2,016 kWh/year for water heating translating to 228.6 million tons CO2 or 6 per cent of total fuel based CO2 emissions (Kemna et al., 2007). However, the governments in cooler climate are following numerous region country specific policies to promote the use of energy efficient water heating and solar water heating systems. For example in 2005, the UK made it a mandatory requirement to replace old boilers with new, more energy efficient condenser types.
In 2004/05 there were 236 million water heaters installed in the EU, of which 2.6 million (1.5 per cent) are based on district heating, 87 million are linked to a central heating boiler and 146 million are dedicated water heaters. 32.4 per cent of households owned a secondary water heater. The 191.4 million households in the EU25 consume a per-household average of 2,016 kWh for water heating translating to 228.6 million tons CO2 of about 6 per cent of fuel related CO2 emissions. With BAT for water heating energy efficiency improvement can be over 60 per cent in the EU bringing carbon reductions per unit in the same order of magnitude (Kemna et al., 2007).
Residential water heaters supply hot water to almost all 87 million single-family homes and over 22,000,000 multifamily homes in Canada and the United States. Since some homes contain more than one heater, there are over 110,000,000 water heaters in use in North America. About half of all homes are served by gas water heaters and another 40 per cent by electric. Traditional storage water heaters (tank style) make up about 97 per cent of the market. Tankless models are slowly gaining market share; gas tankless models accounted for 3 per cent of all units sold in 2006 (US DOE, 2009).
Some 30 million water heaters are more than 10 years old and nearing the end of their life. Each year, about 8 per cent of households replace their water heaters. Between 7 million and 7.8 million water heaters are replaced in the United States annually. Another 1.2 million to 2 million units are installed in new homes. Currently, efficient EnergyStar models account for only 6-7 per cent of sales and less than 1 per cent of the installed base.
A combination of energy saving technologies has the potential to save 741.29 terawatt hours through 2025 or 5 per cent of projected demand for residential and commercial buildings in 2025 (AEEE data and own calculation). If all homes were installed with EnergyStar models, 108-118 billion kWh could be saved (EnergyStar data), which translates to an average of 67,040,956.72 tons of CO2 equivalent savings.
Centrally planned Asia and China
In terms of solar thermal installed capacity China is by far the leader, due to low costs and government support. The EU-27 is the second largest market, with the majority of installations located in the south. In future falling technology capital costs and increasing efficiencies will soon make solar water heating systems economically attractive for a broader range of climates. As a result, global capacity is forecast to double to 975 GWth by 2030, with China still holding 50 per cent, followed by India with 10 per cent (Bloomberg, 2011).
Furthermore, introduction of energy efficiency standards can push the development of more efficient water heater in China. The country generates its electricity dominantly by firing coal, which is a carbon intensive fuel. Appliances are also run on carbon intensive energy sources such as coal-fired electricity and gas. Appliance standards and labelling programs can help mitigate air-pollution problems. The US Department of Energy (DOE) projects that improved efficiency among electric appliances and gas water heaters will reduce CO2 emissions by more than 300 million tons carbon equivalent between 2000 and 2020 in China (Fridley et al., 2007).
A strategic policy package would be needed to tackle the barriers and foster market transformation. Some policy instruments, which have been implemented in different countries, will also be discussed here. In most cases there is more than one obstacle that will hinder the development and rapid market penetration of solar water heaters. This is the reason why it is necessary to implement a combination of instruments to accelerate the transformation to efficient soalr water heating technologies. The following are examples of few successfully implemented policies.
Starting as early as 1974, Barbados has managed to develop a solar water heating industry and the use of solar water heaters in about 40 percent of all its households today. This is around 70 percent of the households that have water heating at all. A combination of fiscal incentives enabled this success:
The simple payback period for homeowners and hotels is less than two years when replacing electric water heating. Cumulative energy cost savings to building owners had already exceeded tax incentives by a factor of 12 in 2003. Oil cost savings to the national economy were already higher than the cost of the solar water heaters by then, with further savings to be expected over the useful life of the water heaters. Please refer to our policy example for more information.
ROSOL (Programme de promotion des CES, promotion programme for SWH) is a programme for the development of the Tunisian solar water heater industry in order to replace fossil energies, in particular liquid petroleum gas (LPG), which is highly subsidised by the government. The programme includes several incentives for suppliers as well as for residential households as end-users.
In the case of suppliers, PROSOL provides a VAT exemption for finished or semi-finished products and raw materials, as well as from customs duties, as they are deemed as imported products or raw materials. Additionally, there is a top-down and bottom-up quality assurance system for suppliers and their products marketed within the programme framework to ensure aftersales service and improve the public image of the solar water heater. Regarding the end-users, PROSOL includes the provision of a direct public subsidy for buying a solar water heater. Furthermore, for the remaining costs of the solar water heater, approximately 80%, PROSOL provides direct and simplified access to bank financing with credit recovery over 5 years via the electricity bill. Please refer to our policy example for more information.