Europe has long had initiatives in place that focus on efficient heat generation from renewable sources. With environmental and geopolitical concerns now at the forefront of energy policy, those initiatives are quickly crystallising into firm commitments to providing energy from sources such as solar and geothermal.

Heat makes up 50 per cent of all energy consumed in Europe. Australia, by comparison, consumes less as heat, although in Victoria, heating and cooling account for approximately 50 per cent of total stationary energy use. Of that, approximately 10 per cent requires a high temperature, which could potentially be generated from a combination of biomass and geothermal technologies. The remaining 40 per cent requires a lower temperature that could be delivered by available solar thermal technology.

European drivers of renewable heat generation

In Europe, renewable heat generation is driven primarily by two considerations. Firstly, that renewable electricity and building energy efficiency alone will not deliver CO2 reductions needed to meet targets; and, secondly, the energy security concerns arising from the geopolitical volatility of oil and gas supplies.

The interruption to natural gas supplies in the Ukraine in January 2006, and the temporary closure of the oil pipeline to Belarus in January 2007 has led to increased concerns of heating fuel supply. Whilst supplies to Europe were only briefly interrupted, both events received significant political and media attention.

Sales and market drivers

Three million square meters of solar collectors are installed in Europe. In 2006, solar thermal markets in Europe were being driven by Germany and Austria, which is similar to the market for renewable electricity. 2007 German figures indicate a 33 per cent drop in sales, leading to a decline in sales in Europe of 10 per cent. A reason behind this was a lack of certainty around the design of support schemes. As a result, the European Solar Thermal Industry Federation has urged “policy makers to put an end to stop-and-go support“, stating that “the industry needs a stable support framework for solar thermal”.

Policies

European Union The European Union sets policy directives for member states. A recent proposal requires members to set targets for renewable energy supply in all sectors (transport, electricity and heating and cooling) to meet the overall energy target of 20 per cent of renewables by 2020. The directive had been introduced in conjunction with similar targets for emission reductions, energy efficiency improvements and biofuel usage.

Individual country policies

The Spanish Building Code was modified in 2006 to include solar water heating requirements in all new buildings. It also regulates energy efficiency for all buildings, lighting and heating equipment and solar photovoltaics on certain buildings.

Portugal recently passed a similar but less complex building code while longstanding Israeli solar ordinances have resulted in 85 per cent of water heaters being solar, supplying an estimated three per cent of total primary energy.

In December 2007, the German government announced a renewable heat law to increase renewable heat generation from 6 to 14 per cent by 2020. The law includes a renewable heat obligation for house owners, increases financial incentives through upfront capital grants and public loans, and strengthens district heating grids. Baden-Wurttemberg became the first German state to introduce the obligation, where all new buildings must generate 20 per cent heat via renewable sources and renovations a minimum of 10 per cent.

New Technologies

Space heating and hot water ‘Combisystems’

Heating water for domestic use has the highest market penetration of all solar thermal technologies. Combisystems, which account for 40 per cent of collectors sold in Germany, are dual purpose water and space heaters. A drawback is that most of the heat is needed during times of low solar energy. Consequently, if the collector is sized to give a reasonable amount of energy in winter, there is energy wasted in summer. Two new technologies are being developed to utilise this wasted heat – solar cooling and seasonal heat storage.

Solar cooling

Heat from solar collectors can be used to provide cooling. One example is the use of absorption cycles similar to those found in gas fridges. Higher temperatures from the solar collectors provide more cooling, so evacuated tube collectors and concentrating trough collectors are important in this application. While currently expensive, there are a number of solar cooling machines now produced in China and Europe that are suitable for small commercial cooling requirements.

Seasonal heat storage

Storing heat for long periods allows excess heat in summer to be utilised in winter. Most stores use water as the medium, sometimes in large underground tanks. In Chemnitz, Germany, heat is stored in an eight million litre underground water tank.

Solar heating in summer is also used to reheat underground aquifers that have heat removed in winter by heat pump systems (vapour compression refrigeration cycles) to produce heat for space heating. In Haarlem, Netherlands, 2,900 square metres of collectors are installed on nine blocks containing 382 apartments. The surplus solar heat in summer is stored in the central aquifer at a temperature of 45°C. In winter, the heat is extracted and used for preheating and as a heat source for the pumps.

There are also systems that use the earth to store heat. In the Drake’s Landing development in Alberta, Canada, water heated in collectors on each house is then circulated through pipes in an insulated area of the ground in summer. In winter, this flow is reversed to extract heat used in the dwellings’ space heating radiators.

Solar thermal industrial process heating

More than 80 operating solar thermal plants for industrial applications have been reported by the International Energy Agency Solar Heating and Cooling (IEA SHC) program up to October 2006, with an installed capacity of about 24 megawatt thermal (34,000 m2). The majority of plants are found in dairies, car washing facilities, and factories with metal treatment, textile and chemistry applications. This market developed after the advent of cost effective collectors that operated efficiently at temperatures of 80° to 150°C.

Photovoltaic/Thermal systems

A photovoltaic/thermal (PVT) system combines photovoltaic cells with a solar thermal collector into one device that converts solar radiation into electricity and heat simultaneously. This allows excess heat generated in the PV cells to be converted into useful thermal energy. As a result, PVT systems generate more solar energy per surface area than separate photovoltaic panels and solar thermal collectors. PVT systems can be used in any situation where conventional solar thermal collectors and PV panels are used. These systems are still at the research stage and are being developed under the IEASHC program.

Lessons and opportunities for Australia

While Australia does not have the same building heat loads as Europe, there are still considerable amounts of energy used as low temperature heating and cooling in buildings and in industry. Consequently, the Australian renewable heat energy industry should be closely watching developments in policy and technology in Europe

Australia’s renewable energy target is generally limited to electricity supply. Solar water heating is included in MRET as a displacement method for electricity supply – despite the fact many solar water heaters displace gas. A more comprehensive target covering heat would allow alternative technologies such as solar air heaters and solar cooling technologies to be included – as well as biomass and geothermal heating.

Solar cooling technologies can provide not only energy and Greenhouse pollution savings but can also displace peak electricity demand. Australian industry and researchers should contribute to international collaborative projects through opportunities such as the IEASHC – so that technologies and market deployment actions are informed by leading thinkers – and Australia has opportunities to develop international markets in the Asia Pacific region.

About the authors

Ken Guthrie Chairs the International Standards committee on solar water heaters and represents Australia on the Executive Committee of the IEASHC Christian Bertsch spent the last six months of 2007 representing Sustainability Victoria and Invest Victoria in Europe.

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