Solar Heat Applications

Heat accounts for a large portion of the energy needs of a building. In an average home, this portion can be as high as 80%. The availability of solar heat depends, clearly, on the sun. In Ireland, we have a solar resource comparable to that in Germany. The use of solar heat relies on heat storage because solar energy availability fluctuates both from day to night, seasonally and as a result of the weather. It is important that any energy available is collected and stored so that it can be used when heat is needed.

There are a number of points to check before investing in a solar thermal system, and cost-effectiveness must be kept in mind at all times.

Solar thermal for hot water

This is the most common use of active solar heat technology. In domestic situations, solar thermal can provide 50-60% of the annual hot water requirement of the dwelling.

Solar thermal for space heating and hot water

In buildings where the heat demand is low, then solar heat can be used to provide a considerable portion of the overall heating and hot water requirement (20-40%). A low-temperature heat distribution system such as underfloor heating is advantageous when using solar thermal for space heating, as it does not require high temperatures, and therefore solar can provide more useful heat.

It is as simple as this, wherever there is a demand for heat, then active solar thermal applications can be investigated.

Solar heating at home

The most common application of solar thermal energy is solar water heating. Solar panels, generally located on a south-facing roof, transform solar radiation into heat. The heat produced during the day is stored in a large hot water cylinder, so that it can be used at any time. Solar water heating systems are generally sized to cover 50 to 60% of a household's hot water (about 1 to 1.5 m² of solar panel per person; 50 litres of water storage per m² of panel). Such a system will provide almost all of your house's hot water needs during the summer, and will cost between €4,000 and €6,000 to install. The greater the demand for hot water, the more beneficial solar thermal will be, and the shorter the return on investment.

A solar combi-system is based on the same type of components but sized to make a useful contribution (30 to 40%) to total heating requirement of the house (space and water heating). For an average house, this requires between 10 and 20 m² of solar panels and a storage tank of 800 to 1,500 litres. The sizing and design of a solar combi-system requires a careful analysis of the heating requirement of the house by an experienced technician. The cost to install a solar combi-system ranges between €8,000 and €15,000.

As it is not feasible to depend on solar energy at all time inIreland, a solar water heater or a solar combi-system needs a back-up heating system such as a boiler, a heat pump or an electric heater.

Further information on solar thermal products and grants can be found in the Better Energy Homes scheme section.

SEAI's Solar Thermal Benefits Calculator helps you in assessing the economic and environmental benefits of installing a solar thermal system in your home. It also provides guidelines with regard to system sizing and costs. SEAI REIO has a free information pack which includes information leaflets, buyers' guides and DVD which can help consumers make an informed choice when deciding to change to a renewable technology in their home. To request your free pack please call 023 8842193 or e-mail renewables@reio.ie.

Solar heating at work

While solar thermal systems are most common in homes, the same technology can be applied cost-effectively for larger applications where there is a significant demand for heat. This is especially the case where the heat demand is high during the summer when the solar output is at its highest. Hotels, swimming pools and sports centres are particularly interesting from that point of view. Buildings or other applications where there is a consistently high hot water demand all year round are also good cases for solar thermal e.g. nursing homes, spas, milking parlours, etc.In large applications, active solar thermal systems are generally designed to cover 30 to 40% of the heat demand. As the price of energy continues to rise, a solar water heating system can reduce your running costs and provide an excellent return on investment for your business.

For further information, we recommend you to order a free copy of SEAI REIO's Procurement Guidelines by sending an email to renewables@reio.ie with your full contact details. See Solar Thermal Info/Resources for further useful information.