Let the sunshine in!
Solar Energy in Ireland is not a myth! We do get enough sun to make Solar an option.
Ireland’s solar climate is as good as Paris and 70% of the solar climate on the Mediterranean coast. In Ireland a horizontal surface of 1sq.meter receives an average of approximately 1100 Kilowatt-hours (kWh) of solar energy per year (the equivalent of 120 liters of oil)
Solar energy in Ireland is provided by both direct sunlight (40%) and indirect sunlight (60%). So, even when the sky is overcast, its radiation (light) is available at ground level and can be converted into useful heat by a solar water heater. With the right policy framework, solar energy could account for 10% of renewable energy generation capacity by 2020 – representing 500MW of installed generation capacity (ISEA)
“In 90 minutes, enough sunlight strikes the earth to provide the entire planet’s energy needs for one year.” – IEA
Solar energy, through different techniques, can help produce energy or heat buildings and water.
Solar water heating systems are either used just for hot water or for heating and hot water. There are two main types of systems: flat plane solar thermal and evacuated tube.
Photovoltaics and Concentrated Solar Power (CSP) systems harness the heat from the sun and use it for creating electricity. PV panels directly convert the light into electricity while CSP use mirrors to redirect the sunlight from a larger area onto a small area, either a tube or a solar power tower. Through this the sunlight is used to heat water to produce steam that runs a turbine and a generator to produce electricity.
The first concentrated solar power station was built in Maardi, Egypt in 1913.
What can solar power be used for?
- Passive solar gain – refers to the direct effect of the sun on buildings – big, wide windows permit solar heating to enter and warm the rooms.
- Solar water heating (solar thermal):
- Solar thermal for hot water – This is the most common use of active solar heat technology.
- Solar thermal for space heating and hot water – In buildings where heat demand is low, solar heat can be used to provide a considerable portion of the overall heating and hot water requirement (20-40%).
- Photovoltaics (PV) panels
- Concentrated Solar Power (CSP) – Solar power plants
What happens when it is cloudy?
Solar panels work both on sunny and cloudy days. They not only harness direct sunlight when the sky is clear but also diffused light on the cloudy days, so you will still be generating electricity thought not as much as on a sunny day.
How can solar energy be stored for later use?
One of the problems with solar energy is that it can be intermittent, depending on the climate or time: sunny or not, day or night. The solution to this is energy storage and although it is still a new topic we can see many advances in this area of research.
- Today, energy storage is done through batteries and they can range from a simple car battery to more sophisticated backup systems.
- Another solution is ‘net-metering’. In general terms this means using the electricity grid as a storage option. So, owners of solar panels can feed the extra electricity generated during sunny days into the electricity grid and then, during the night or on cloudy days, use electricity from the grid. The downside of this is that the grid supply is generally from power plants using fossil fuels.
- Solar powered pumped hydro storage systems solves this issue. How does this work? During low demand periods, the excess of solar electricity is fed into the grid from where a pumped hydro system uses it to pump water from a lower reservoir to an upper one. During high demand periods or when there is no sun the water from the upper reservoir is used to produce electricity.
How much will my PV panels save me?
According to Irish Solar Energy Association a 1kilowatt solar PV system can produce around 850kWh (units) of electricity per year in Ireland, meaning that a 2kW system is able to produce around 1700kWh, almost half of the annual electricity consumption per average household.
How much will my solar thermal system save me?
A solar thermal system can provide hot water all year round: 90 to 100% in summer, 60 to 70 % in spring and autumn and 10 to 20% in winter. On average this means between 60 and 70% of your hot water heating costs. For a household of 5 people, this equates to about 350 to 500L of oil or 3200 to 4000 units of electricity.
What is the payback time on the solar thermal system?
For an Irish household of 5 people, that is replacing an oil or gas water-heating system, the solar thermal system has a payback of about 6 to 8 years. If the heating system is electric, the payback is between 4 to 5 years.
How efficient are solar panels?
Solar panels have efficiency between 11 and 15%, depending on the manufacturer.
Advantages of solar panels:
- The resource is free and produces no greenhouse gases;
- The panels can be placed on buildings, so no extra space will be used for their installation;
- They require little maintenance;
- Solar panels are suitable for remote locations where access to the grid is difficult;
- Solar panels are suitable for both urban and rural areas;
- Each square meter of PV panel will prevent approximately 1,500 kg of CO2 emissions over a 25 year lifetime (this includes the CO2 emissions avoided by exported energy).
Ireland has a solar resource comparable to that of Germany (SEAI). In 2014 solar power in Germany accounted for 6.2% of total energy generated.
What types of PV panels exist?
- Crystalline – Monocrystalline – Monocrystalline cells are cut from a single crystal of silicon and are the most efficient type of cell, but also the most expensive to produce. They are completely rigid and must be mounted in a rigid frame for protection.
- Polycrystalline – Polycrystalline cells are made from a slice cut from a block of silicon that consists of many crystals. Solar PV panels made from these types of cell are slightly less efficient but cheaper than monocrystalline cells. They also need to be mounted in a rigid frame.
- Thin Film – Amorphous – Amorphous cells are manufactured by placing a thin film of non-crystalline silicon onto a wide range of surfaces. This creates the least efficient type of PV panels but also the cheapest and if manufactured on a flexible surface, the whole PV panel can be flexible. One problem with amorphous cells, however, is that their power output reduces over time, particularly during the first few months, after which they become stable.
What types of solar thermal system exist?
Flat Plate Collectors:
- Building-mounted flat plate collectors can be positioned both “in-roof” and on-roof due to their structure (heavy, rigid, robust box-like structure). The efficiencies of flat plate collectors make them very suitable for domestic installations or for installations where very high temperatures aren’t required. They are often considered to be more optically appealing due to their flat surfaces, but this is a matter of personal choice.
Evacuated Tube Collectors:
- Building-mounted evacuated tube collectors can only be mounted on-roof due to their lightweight structure, which is most commonly individual tubes mounted on a frame. On average, an evacuated tube collector will provide approximately 20% more yield per m2 of aperture area than flat plates, which means that less installed area is required for similar heat outputs. High efficiencies from low radiation and high temperatures (very useful where high temperatures are needed in process/industry) (SEAI).