Renewable Technologies

Solar Thermal

Solar thermal or solar hot water systems use a heat collector, which contains a fluid, usually water or antifreeze, which is heated by the sun. The heated liquid then passes through a heat exchange coil in the hot water cylinder where the heat is transferred to the cooler water in the lower part. The system may have a back up system which heats the water to the desired temperature and also in times of low sunshine or high demand. Solar thermal systems reduce the consumption of fossil fuel for domestic heating and can typically provide about 55-70% of a household's hot water requirement. 

A solar water heater can suit most situations provided the following requirements exist:

• Space to put the solar panels (generally on the roof) and room for the storage cylinder in your utility room or hot press.
• Access to the sun for the panels (orientated between south-east and south-west) and no over-shadowing by trees or other buildings.

It is important to seek the correct advice and a reputable supplier and installer prior to fitting any sort of solar heating system. They will be able to provide advice on the type/size of the system required, the accreditation/certification of the system, and any other information required.

Solar Electric/ Photovoltaic

Solar electricity systems convert sunlight directly into electricity through the use of photovoltaic cells (PV) located in panels. The light, which shines on the PV cells, creates an electric field, which causes electricity to flow. The greater the intensity of the light, the greater the flow of electricity. Voltage is created when light shines on the panels, which produces a direct current, which is then converted to alternating current and fed into the dwellings main electrical system. In Ireland a square meter of ground will receive 1000KWh in solar energy each year.

Heat Pumps

A Heat Pump does not look very different from and can perform the same functions as a conventional gas or oil boiler (i.e. space heating and sanitary hot water production). It does it much more efficiently, however, as it uses most of its heating energy from free renewable sources.

While renewable heat pumps for space heating are best suited to new houses with high levels of insulation and low temperature heating systems, they can also be used to retrofit or replace existing heating systems. For example, in Sweden 50% of the replacement of existing heating system is done with renewable heat pumps. When a heat pump is installed it is usually connected to the existing central heating system and can supply most of a houses heat requirement (70 to 90%). During very cold periods of the year, the existing boiler takes over and provides the higher temperatures required in the heat distribution system.

Heat Pumps extract low temperature heat from the ground or air and transfer it at a higher temperature to the space heating or water heating system. This is achieved by using antifreeze, which has a high temperature range and works on the same principle used in fridges. The low pressure cool antifreeze picks up heat from the ground and then releases the heat when it is forced into higher pressure. A typical ground source heat pump will consist of a heat collection loop of plastic containing antifreeze solution, a circulating unit, a heat pump, and a space heating system. Heat pumps can consist of either vertical loops lowered deep into the ground or horizontal ground collection systems buried in approximately 1m of soil.  

While heat pumps in residential buildings are usually more expensive initially to install than other heating systems, their greater energy efficiency allows the extra cost to be recouped in a few years - typically between 3 and 8 years. After that, it is possible to make large savings in energy and maintenance costs compared with conventional heating systems.

In commercial buildings, the initial cost of a heat pump is often competitive with conventional heating and cooling systems (typically boilers, air-conditioning units and cooling towers). However, when properly designed and integrated into the building, heat pump systems can yield a simple pay-back period of 5 years or less when compared with conventional systems.

Biomass - Wood Chip / Wood Pellet

Biomass is organic matter that can be burned to produce heat. The process creates steam to turn turbines and, ultimately, produce electricity. Some of the most common examples of biomass are agricultural crops and residue, wood and wood waste, animal and municipal waste. Liquid biofuels can also be derived from biomass crops such as oilseed rape.  Biomass can be converted to different forms of energy including heat, power, combined heat and power (CHP), or liquid biofuels.

Biomass or wood fuelled systems, which can burn logs, wood chips or wood pellets from sustainable forests, can be considered a clean and highly efficient alternative to fossil fuel systems.  The two main types of biomass heating devices are radian heat stoves or boilers. They can be used to provide space heating or a combination of space heating and hot water. The occupants of a house which uses a biomass system can benefit from lower energy costs, secure supply and overall clean, environmentally friendly fuel, as wood chips and wood pellets are carbon neutral. A typical house would require between 4 and 5 tonnes of pellets per year or 8 tonnes of wood chips. It is important, therefore, to take the provision of bulk storage into account when designing/building for such a system. 

Heat Recovery Units

Heat recovery ventilation can reduce costs for heating and can replace existing regulatory ventilation. This enables your building to retain heat and occupants benefit from a healthy, balanced and fresh airflow. The energy contained within the warm waste water stream (e.g. showers, washing machines and greywater) can be recovered by using waste water heat recovery units. In this way you are reducing the heat requirements for both domestic hot water and ancillary equipment needs.

Wind Turbines

Wind turbines harness energy from wind and convert it to electricity. Wind causes the blades to rotate; this turns the blade rotor axle, which passes through an electricity generator. The generator is connected to the dwelling’s mains electrical system. Generally, wind turbines yield maximum power during winter when a dwellings demand is typically highest but the yield can be variable over the course of a day. When mounting a wind turbine on a building it is important to:

• Locate as far away as possible from major wind spoiling features, such as trees or adjacent buildings
• Locate on the side of the building that faces the prevailing wind and away from chimney or flues
• Locate as high as possible

The installation of a wind turbine on your home or on your land usually requires permission from the local authority, so it's important to always check with your local authority about planning issues before you have a system installed.

Further information on renewable energy technologies can be found at www.seai.ie.