Paul Dykes Paul Dykes
  • Solar
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The Sun in Action

The Sun In Action

Since the beginning of time, the sun has been the source of energy and life on earth. It is in effect a huge nuclear reactor, at 6,000 ºC, which provides our planet with heat and light. Today, solar energy can provide cost-effective solutions to fight climate change and reduce our dependency on expensive and polluting fuels.

Solar energy in Ireland is not a myth, and contrary to what many people may think, we are not short of solar energy resources. In fact every year from the sun Ireland receives the equivalent to 600 times the total amount of energy we consume annually.

At current energy prices the average Irish family will spend over s40,000 in the next 30 years to heat their home - reducing that bill by over 50% can be achieved cost-effectively by harnessing the energy from the sun. This very intense source of free, eco-friendly energy will always be available - it is carbon dioxide free and will never send us a bill.

Commercial and public buildings represent 15% of Ireland’s total final energy consumption and emit over seven million tonnes of carbon dioxide every year (one fifth of Irelands total). Nearly 70% of that energy consumption is on cooling, space and water heating. We will see how they can also benefit greatly from using solar energy.

Let the sun shine in

Solar Hot Water (c) Christopher Drake. Courtesy of DOE/NREL At a time when thousands of new homes and commercial premises are being built to satisfy the current economic boom, it is worrying that many of the properties fail to meet basic design principles that could cut energy consumption by over 30% at no extra capital cost. Whilst building regulations ensure reasonable standards of insulation, most homebuyers are unaware that with just a few simple, common-sense measures houses could make far more efficient use of natural solar energy.

Passive solar design is an architectural approach that seeks to maximise solar gains, reduce heat losses and provide for natural ventilation and daylighting. Key elements of a passive solar building is south orientation, a high level of insulation, a comparatively large area of glazing on the south façade, controlled ventilation, shading to avoid overheating, wind sheltering, etc. The use of sustainable construction materials has also to be taken into consideration when designing and constructing a building. Overall passive solar design ’s uses building materials, orientation and general design to ensure solar gains are maximised. need not add anything to the cost of the building and produces a more pleasant and healthier living or working environment.

The application of passive solar design is an integral part of the overall architectural project for the building. The architect is the one who will help you to undertake it from design until commissioning of the building. Applying passive solar design is part of an overall objective of quality in architecture that involves suitability for use, durability in performance and comfort. The real key to passive solar design is to build south facing homes, position frequently used rooms on the south side, avoiding overshadowing from adjacent buildings and use `green` building materials use brick and stone which store day time heat and release it slowly at night.

Collecting solar energy for space and water heating

An active solar thermal system relies on solar collectors to transform sunlight into heat that then can be used for space heating or more commonly producing hot water. 2.5 million households use solar water or air heaters across Europe and the solar thermal market is rapidly increasing in Ireland. In 2001, a network of professional installers in Ireland installed over 200 solar water or air heaters - that figure will at least double year on year for the next ten years.

High quality products are now available, solar systems are reliable and their productivity can be guaranteed. For an investment of between s3 and s5,000 euro a solar water heater will effectively reduce the average hot water bill by over 50%. Solar thermal collectors can also be used in a larger system that combines space heating and domestic hot water production. A so-called solar combisystem can cost between s8,000 and s10,000 and reduce your total heating and hot water bill by 40%.

Solar water heaters are ideal for new houses or extensive
renovations as their installation can be integrated in the overall building work - roofing, plumbing, heat engineering, etc. This will reduce significantly the extra-cost of the equipment as some elements of the solar water heater can be discounted against a new conventional system (hot water tank, regulation, roof cover, etc.).

Once correctly installed, a solar water heater requires very little maintenance and in normal conditions, rainfall ensures clean solar panels. A solar water heater is manufactured and installed to last and their average lifetime is 25 years or more.

A solar heating system always needs a complementary source of energy in order to ensure that the heat required is supplied at all time. Instead of using an oil or gas boiler as a back-up, you can choose to combine your solar system with a wood boiler or a heat pump in order to maximise the environmental and financial benefits of your investment.

Renewable heat pumps - better by nature

PV system for a home (c) Warren Gretz. Courtesy of DOE/NRELA renewable heat pump harnesses heat from solar-derived sources (ground, water, air) where it is freely available in large quantities at a low temperature. The heat pump will concentrate that heat, upgrade it to a higher temperature and release it when and where required. The magic in it is that for every unit of electricity used to operate the heat pump - over four units of heat are generated.

In both domestic and commercial buildings, energy demand is dominated by heating requirements - ground source heat pumps are one of the most efficient ways to heat space and sanitary hot water, and eventually cooling. This well established technology offers benefits for all ranging from a healthier and more comfortable working and living environment reduced energy consumption and avoided greenhouse gases.

In excess of 1000 ground, water and air source heat pumps are in operation in Ireland and this number is set to more than double in the next two years. By comparison, over 30,000 ground/water source heat pumps were installed in Sweden last year.

Heat pumps are generally more expensive to install than conventional heating systems. But the extra cost for the initial investment (3 to 5,000 euro) will be rapidly recovered by your energy savings, typically between three and eight years if you compare with an oil boiler.

The figure below compares the heating cost of several modern heating systems to provide space heating and hot water in a 200 m2 house (20,000 kWh of heat per year). A ground source heat pump can provide financial savings of up to 70% on energy bills and maintenance costs.

Ground or water source heat pumps also make sense in commercial or institutional buildings. When properly designed and integrated, heat pump systems can yield a simple payback period of five years and sometimes less compared to conventional systems. If there is also a demand for cooling in the building, the initial cost of a heat pump system can be competitive with conventional HVAC systems and the operation costs are significantly lower.

The new Motor Tax Office building in Tralee is a good example of solar energy in action. This well insulated building eases the burden on the heating system and a ground source heat pump draws energy from the ground to provide heating in the winter and deposits excess heat to cool the office in the summer. In addition to the ground source heat pump, an array of roof-mounted 15 m2 solar collectors provides hot water for washrooms. Other energy efficient features include an automated natural ventilation system, highly energy efficient lighting and an energy management system. A recent independent energy survey concluded that the annual energy costs for the new building are over 2,500 euro less than an office of similar size and use.

The Renewable Energy Information Office is a service of Sustainable Energy Ireland (formerly the Irish Energy Centre). Its objective is to support the development of renewable energy in Ireland by providing independent and expert advice as well as information on related financial, environmental and technical issues