Solar For Existing Homes and Businesses
Before you choose solar, try to reduce your energy consumption by making your home or business more energy efficient. In many cases, installation of energy efficient bulbs, appliances and proper insulation can result in very large reductions in energy use. Depending on how much electricity or hot water you want or need to produce, an appropriately sized solar system can then be chosen. We recommend a WOW energy assessment which will provide you with a report, the purpose of which is to enable you to look at cost effective methods of improving the energy performance of your home or business.
 
Solar is a clean, renewable form of energy generated from the sun. It doesn’t produce any harmful emissions such as CO² so using it will benefit the environment. Over three million households across Europe already use solar systems.

Solar Water Heating
Solar water heating systems for domestic applications have three main parts; a solar collector (solar panel), hot water storage cylinder and a pump. There are two main types of solar hot water collector, flat plate and evacuated tube. The flat plate collector looks like a thin, large rectangular box with a transparent cover. The sun heats the absorber plate which is usually black metal which in turn heats fluid running through pipes within the collector. The heated fluid then moves, either using gravity or a small pump, to the storage cylinder. Evacuated tube collectors work in a similar way. These consist of an array of evacuated glass tubes each containing an absorber tube which transfers heat to a transfer fluid. The vacuum created in the manufacturing process of the tubes greatly reduces heat loss from the system as there is no air to conduct heat away.
 
The hot water storage cylinder is larger than a normal cylinder, usually holding 300 or 400 litres of water. The cylinder is insulated to a high standard and requires more space as a result.
 
For commercial or other applications (ie swimming pools) the best type of collector will depend on the specific situation. For example an out door swimming pool can have it’s water temperature raised by a few degrees in the summer by the cheapest panels on the market. At the extreme a bed and breakfast wanting to supply all guests with enough hot water with need highly efficient and correctly sized panels that cost more.

How Many Panels?
An approximate rule is 1m² of evacuated tube panel per person or 1.75m² of flat plate collector per person using your property.
For commercial applications WOW recommends having an individual assessment done to correctly size the system.

Siting
Ideally panels should face south; but south-east or south-west will still produce good results. The panels can be mounted on the main property roof, a shed roof, floor mounted or in some cases wall mounted. There will be some heat loss if the system is positioned too far away from where it is to be used.
 
Flat plate collectors can be installed “in roof”, this means that as a roof is being tiled an area is left un-tiled and collectors are put in place with flashing around them.
 
Planning permission may be necessary in some areas if the panels are visible.
 
The size and weight of the water storage cylinder should be taken into account when thinking of its positioning. A full 400 litre cylinder will weigh approximately half a tonne!

Payback, Maintenance and Grants
The payback period will depend on how efficiently the system is being used, how much it costs and how well it was fitted. If the number of panels is correct for the needs of the property, they are fitted correctly, then payback can be as little as five years. In most situations between five and ten years is accurate. They require very little maintenance and most systems are guaranteed for 10 years. Their lifetime is about 25 years.
 
Grants through www.sei.ie are available for some solar systems. Wow can help with grant applications; the product must be registered with Sei as must the installer to avail of the grant. €300 per m² to a maximum of 12m² is available at present.

Solar Heating
In a solar central heating system, the heat generated by the solar panels is used to warm up water stored in a large tank. The heated water is circulated into radiators or under floor heating to distribute warmth around the house, and is also used to produce hot water for bathing, showers, etc. A control system ensures the regulation and safety of the whole equipment. A solar space heating system is generally designed to cover between 30% and 40% of the annual space and water heating requirement; this can reduce fuel bills by a similar amount.

Solar Air Heating
For comfortable and healthy living, homes require heating and ventilation. Solar air heating systems use air instead of water to circulate the heat collected by roof mounted solar panels in order to provide space heating and ventilation simultaneously. They are particularly effective in well insulated houses which are built airtight and, when used in combination with a heat recovery ventilation unit can reduce heating bills considerably.
They can also be used to produce hot water through an air-to-water heat exchanger.

Solar Electricity
Photovoltaic (PV) is a growing technology. Photovoltaic solar cells convert sunlight into electricity. They are made from semi-conducting materials such as crystalline silicon. They are quite often seen in garden lighting, calculators, traffic warning signs and pond water fountains. They can also be used in greater number to provide homes and businesses with electricity. When used for domestic or commercial applications the PV system has four main parts; PV modules, DC-AC inverter, controller and battery store.
Groups of PV cells are electrically configured into modules and arrays, which can be used to charge batteries, operate motors and to power electrical loads. With a converter PV systems can produce alternating current (AC) compatible with conventional appliances.

Siting
PV is silent and has a low visual impact so is suitable in most areas (check local planning regulations). PV can be installed on or “in” a roof on or near to the house. The modules must not be in shadow and work best if south facing; but will still produce 80% of the optimum output in an east or west position.

How Many Panels?
WOW recommends an individual assessment of needs as cases and requirements vary greatly. In some cases stand alone systems work best and can be tailored to an individual piece of equipment or building i.e. a remote cottage. These can sometimes be more cost effective than extending existing power lines. Solar can work very well to provide a “total” solution when combined with wind energy. Start looking at your energy usage and how much you can cut down, then how much you would like to produce.

Payback, Maintenance and Grants
The price of photovoltaic modules is initially expensive; but it is a safe reliable source of electricity. It has no moving parts and requires very little maintenance. Most manufacturers will guarantee the PV modules for 20 years.
Unfortunately as domestic users aren’t allowed to sell their electricity directly to the grid in ROI at present PV is not as cost effective as it could be. Taking into account the necessity in most domestic situations to have a battery store to get the most out of the PV module the estimated payback is 10-15 years.
No grants are available on PV at this time.
Information is based on SEI publications available on www.sei.ie 
 

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