Solar Panels

Solar & Renewable Technologies offers a supply and install service for Solar panels, oil and gas boilers, heat pumps, underfloor heating systems etc. in the greater Dublin Area. Our installers are based in Bray (Wicklow), Rathdrum (Wicklow), Naas (Kildare), Trim (Meath) and Swords (N. Co. Dublin)

Note our telephone number has changed to 01-8997133

Site Surveys enquiries to 086-7842808 (John O'Connell)
Management / Scheduling enquiries to 086-3807914 (Fergus Wheatley)
Technical enquiries to 086-8783151 (Niall MacCaughley)
LED lighting enquiries to 087-2349366 (Brian Kelly)

We've written the book on Solar Panel Installations

We have co-authored the Solar Installers Training Manual published by Action Renewables. This manual is now used by the FETAC approved training academies for installers being training to SEAI (SEI) standards. We have also been asked to update the U.K. equivalent BPEC course material.

Summaries of the course material is available on the companion website; Solar Panel Training Manual

Expert Advice & Project Management

Solar & Renewable Technologies provides expert advice to achieve an excellent energy rating for domestic & commercial projects.

We will engage with the Client and the project design team to assist in the design of the best heating system for the Client's desired outcome, be it measured in Environmental terms, Easy of Use, Economy, or indeed a mixture of all three.

The Solar Resource

The amount of energy generated by the sun each year is huge compared to our annual global requirement and is also the primary motive force for the other renewable sources of energy shown below.

The useful potential of these energy sources is dwarfed by the amount solar energy arriving on the planet each year. Unfortunately the energy is dispersed over half the Earth's surface at any time and it varies in intensity from one location to another as weather conditions change. By comparison, fossil fuels possess very high energy densities. Just consider how far a car can travel on a litre of petrol or how a relatively small volume of oil will heat a house for a full year. Matching the convenience and constant availability of fossil fuel systems is a constant challenge to the designers of renewable energy systems, as they try to harness a variable energy supply to satisfy fairly rigid energy demand profiles. In solar installations, system design aims to store sufficient thermal energy for later use, while adapting to daily and seasonal variations in sunshine.

Solar Irradiance and Insolation

Solar irradiance and insolation are measures of the amount of solar radiation energy received on a given surface area in a given time.

Solar irradiance measures the power at any particular moment in watts per square meter (W/m2)

Solar insolation is the energy received from the sun at a given location over a length of time, usually expressed as kilowatt-hours per square meter (kWh/m2) per day or per annum.

The largest radiation values occur over the equatorial zone because the Sun's rays are concentrated on a smaller horizontal area, whereas the lowest values are achieved towards the poles as the solar radiation is projected over a larger area.

Outside the Earths atmosphere the solar constant gives an average irradiance figure of 1367 W/m 2.

The atmosphere absorbs some of this radiation. By the time the radiation reaches the Earth's surface, this value has decreased to about 800 to 1000 Watts on every horizontal square metre on good clear days. This decrease is due to a variety of mechanisms, namely

1. reflection back into space by the atmosphere
2. absorption of energy by various molecules in the atmosphere (see the marked dips in the graph overleaf)
3. Mie scattering by dust and pollutants in the air
4. Rayleigh scattering by interaction with the air molecules

The spectrum outside the atmosphere is often termed AM0 (air mass 0). At the equator with the sun directly overhead, the reduction in light intensity due to passing the shortest possible distance through the atmosphere is termed AM1. Over the course of the year at our latitude, the air mass would vary from a value of about 1.2 in mid-June to about 4 in mid-December. Thus the reduction or attenuation factor due to the Sun' radiation travelling through the atmosphere and being absorbed and scattered, would give have a value of between 20-40% in June and about 50-85% in December.

The Mie scattering component is particularly susceptible to pollution in industrial areas and is primarily responsible for the variations in these total attenuation values. The clean air from the Atlantic that usually sweeps in over Ireland and Britain tends to keep Mie attenuation at the lower end of the above values, except around major cities or when air masses stagnate over the country for appreciable times.

Solar Panel outputs at different angles and orientations

Despite the huge variation between summer and winter energy levels, a significant compensation can be made by the angling of the collector so that equivalent winter shadow lengths are as long as possible. The solar panel is then receiving all the energy in the shadow area and is almost at a right angle to the incoming sunshine.

The graphs below show the expected monthly outputs of a 6 square metre flat-plate panel connect to a 300 litre cylinder. These results were obtained using the T*Sol solar simulation software. (www.tsol.de ).

A steeper roof angle gives substantially more output in the winter, and less in the summer. It can also be seen from the graphs that there is also a western bias. Given a choice of two roofs, a west facing roof is preferable to an east facing one (mainly due to the higher afternoon ambient temperature that reduces collector heat losses).

Generally a flat plate will output about 350 kWh annually for each square metre installed, up to about 6 m2 when connected to a 300 litre cylinder. Diminishing returns are apparent for larger collector areas if they are not coupled with a larger cylinder and matched by a larger hot water demand.

It is also recommended that a minimum 50 litres of hot water storage is available for each square meter of panel.

Flat-plate collector Characteristics:

Zero-loss efficiency 82%
Thermal Loss a1: 3.52
Thermal loss a2: 0.0151

Water Usage: 250 litres per day at 45oC - profile "Detached House (Evening Max)"
Cylinder: 300 litres with 50mm 0.025 W/Km insulation, no gaps.

Pipe run: 16 meters internal 15mm pipework insulated with 19mm 0.045 W/mK insulation. 0.5 meters of external pipe insulated to same standard.

Simulator outputs Month by Month

Winter output is significantly higher on steeper roof angles, and only marginally lower in the winter.

Despite the massive differences between summer and winter energy levels, a significant correction can be made by the angling of the panel so that equivalent winter shadow lengths are as long as possible. The solar panel is then receiving all the energy in the shadow area.

The graphs below show the expected monthly outputs of a Wimex 60 tube system.

Outputs with different cylinder sizes

A 30° roof angle is very common in the UK and Ireland and was chosen to give the most relevant results.

Likewise to compare like with like, the daily consumption was fixed at 250 litres of 45°C water per day. Changing the water consumption both in volume and profile can lead to large changes in system output which overwhelm other system parameters.