The terms solar energy and solar power are often used to describe technologies which collect the energy of the sun and redistribute it for our use. These terms are however a little ambiguous. For example, solar energy effectively drives our whole planet, wind, wave and fossil fuels could ultimately be regarded as solar energy. For the purposes of this site our only concern is for solar energy that can be collected directly by our dwelling and used to, for example, heat water or to drive our electric devices. For this article only Solar Photovoltaic power generation is considered. Please follow the link to take a look at Solar hot water.
| If you are interested, all light is made up of photons, which might be best described as tiny little packets of energy. There is a whole range of different energies or “packet sizes” which if you put them all together from small to large would constitute the spectrum of light. |
| Solar Hot Water... |
To collect solar energy a method is required to collect photons of light and to convert the energy in this light into another form of energy for storage or use.
In photovoltaic’s this energy is directly transferred into electrical energy using solar cells, the energy may then be stored in a battery, used immediately in your house or sold back to the grid.
| In solar cells the light photons are absorbed by transferring electrons in a semiconductor to higher energy levels. They are transferred to what is called the conduction band of the semiconductor, where they can flow through a circuit and provide electrical energy to your property. Semiconductor physics is a bit much for this site; there is a good wiki on the subject. http://en.wikipedia.org/wiki/Semiconductor. |
Is it worth it?
On the face of it, it should be quite straight forward to calculate how sensible an investment in photovoltaic power generation is likely to be. The number of variables is however extraordinary, here are the more important
- How sunny is it where you live.
- The orientation of solar panel, (North, South, East, West).
- The angle of the panel.
- The size of the intended panel.
- The efficiency of the solar cells.
- Efficiency of the electrical systems, (invertors and power storage)
- The cost of the installation.
- The cost of mains electricity.
The first term that you generally come across when looking into solar modules is the term Kilowatt peak (kWp) or peak power. This value specifies the output power achieved by a Solar module under solar radiation under set standard test conditions. Standard test conditions use a solar radiation level of 1,000 watts per square meter (W/m2).
As an example, an 8m2, 1kW peak system (1 kWp) is often specified as an entry level system. This means that under test radiation conditions of 1000 W/m2 this 8m2 panel is capable of producing a 1kW power output. A general consensus of suppliers indicates that such a unit should produce 750 kWh of electricity per year in the UK, if correctly oriented.
The table below give an indication of how these values might be derived and considers different radiation level across the UK, but it is very rough. A payback is also presented to show what happens if the electricity price doubles. If you are interested there is also a solar radiation map of Europe at the bottom of the article.
| Light energy avaiable to you see graphic kWh/m2 per year* | 900 | 1000 | 1100 | 1200 |
| light energy incident on a 8m2 panel * kWh per year | 7200 | 8000 | 8800 | 9600 |
| Light capture efficiency, or Gross efficiency over full area of solar collector | 12% | 12% | 12% | 12% |
| Energy converted to electricity 8m2 collector kWh per year | 864 | 960 | 1056 | 1152 |
| Electrical efficiencies, storage and invertor | 75% | 75% | 75% | 75% |
| Useable electrical energy kWh per year | 648 | 720 | 792 | 864 |
| Equivalent standard rate mains electric price of this energy per year | £ 87 | £ 96 | £ 106 | £ 116 |
| Indicative installed cost of PV system | £ 8000 | £ 8000 | £ 8000 | £ 8000 |
| grant | £ 2500 | £ 2500 | £ 2500 | 3 2500 |
| Payback period (years) | 63.3 | 57 | 51.8 | 47.5 |
| Payback period if energy prices double (years) | 31.7 | 28.5 | 25.9 | 23.8 |
| *The value for the light energy availiable assumes that the panal is optimally inclined at about 38 degrees and is south oriented. | ||||
To determine if a system is financially viable in the UK it is instructive to use the installers own figures, however the installers do not generally state which part of the UK their figures are applicable to, probably Cornwall! Generally a 1kWp system costs about £ 8000, and there are grants available to reduce this to £ 5500. If mains supplied, 750kWh of electrical energy currently cost on average £ 88.50. So irrespective of maintenance issues, cost of financing a project or loss of interest on otherwise invested funds; the unit would payback in about 62 years.
At the other end of the scale a large 40m2, 5kWp system would cost about £ 24000 to install and produce 4280kWh per year, which if mains supplied would cost £ 505. This unit would then take 47.5 years to payback.
I guess you should make your own mind up.
Introduction:
Sustainable energy; Energy is the capacity to do work in today’s terms. Sustainability when used in conjunction with energy can be viewed or expressed as ‘sustainable development’ defined as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’.
Currently we are using and depleting fossil fuel sources that naturally cannot be replaced. Sustainable resources are those which will not be significantly reduced over a long period of time; ie wind, sun (solar), tidal, wave and geo-thermal.
Current energy production and its affect on the environment:
Fossil fuel burning contributes heavily CO2 into our atmosphere, Nuclear energy is potentially dangerous if a reactor were to be damaged however it is the waste material that takes many years to deteriorate to safe levels; hundreds of years, therefore it has to be buried deep underground; non-renewable fuels.
Hydroelectric facilities are sustainable however, large systems have an effect on the local environment; huge damns across valleys holding back millions of gallons of water which has flooded many acres of land. Smaller projects have little or no environmental impact.
Renewable energy sources:
These are sources that will not run out in the future: Solar; used in two ways to product electricity converting sun light through photovoltaic cells and the second method using the thermal effect of sunlight to heat water for the home. Tidal; which can be used to build up a large quantity of water and at low tide, return the water through small turbines to generate electricity. Wave; uses the up and down movement of water to move mechanical devices that turn/transfer the mechanical energy to pump/turn generator of electricity. Wind; used in wind turbines to generate electricity and Geo thermal; uses the heat under the ground to help heat houses and other buildings.
Solar (Photovoltaic) The terms solar energy and solar power are often used to describe technologies which collect the energy of the sun and redistribute it for our use. These terms are however a little ambiguous. For example, solar energy effectively drives our whole planet, wind, wave and fossil fuels could ultimately be regarded as solar energy. For the purposes of this site our only concern is for solar energy that can be collected directly by our dwelling and used to, for example, heat water or to drive our electric devices. For this article only Solar Photovoltaic power generation is considered.
Initial purchase and installation costs can be between £6000 to £18000, producing between 1.5 and 2KW which is an average band requirement for the domestic home, however over supply of power from the panels can be sold to the electric supply grid generating an income for the householder. Excess power can be stored in batteries and used in darkness when the solar panels do not function. This technology can greatly reduce the cost of powering the home and create income therefore paying for itself in as little as 5 years and of course reducing the house carbon footprint as no greenhouse gases or CO2 are generated by this technology.
Solar Panels (Thermal) uses the suns heat to harm water in pipes on the roof which is then pumped into the house hot water tank transferring its energy into the hot water system, the normal system (electricity, gas or coal) takes the temperature up to that set for the water. This method reduces the amount energy needed to heat the water, therefore saving on cost and again reducing the carbon footprint of the home. It is reliant on the amount of light energy incident on the panels; greater exposure will generate more heat and visa versa, and of course it will not function at night (darkness). The cost of purchase and installation is lower than PV (photovoltaic) technology.
Small Wind Turbines are not very common in suburban areas due to the cost of purchase and installation, planning regulations and lack of education in how to use such technology efficiently and which applications are best served. Wind turbulence around buildings causes wind turbines to work erratically and again reduce efficiency. To perform at an optimum level, they need to be mounted at 50 feet or higher above ground level where the wind speed is higher and more consistent, and have direct and unrestricted access to the wind.
Wind power gives clean energy and is cheaper at this time than solar equivalents however, initial capital cost can range from £4000 to £18000 that produce 1.5 to 6 KW of power. These systems operate day and night and therefore have the ability to either store unused power or be sold on to the national grid.
Geo-Thermal is a method of taking heat energy from the ground and transferring this into the hot water system [heating] in a house or building. At a depth of a few metres, the natural heat of the earth is 11 to 12 degrees C and by burying pipes at this level underground, this heat can be pumped up to the surface and into homes. It takes around 1 unit of power to produce 3 to 4 units of equivalent. The system is cheap to run and is easy to install if applied to a new housing development but can be more expensive and disruptive in an existing property.
Diagram 1 Diagram 2
Principle of geothermal heating. Diagram 1: Liquid is pumped into the ground travelling through a return loop back into the house into a heat exchanger. Diagram 2: The heat transferred from the ground [around 12 degrees C] is used to raise the temperature of the heating system from cold and then heating is continued by the conventional system to further increase the internal temperature of the house. This type of system has no visual impact on the house or close neighborhood.
Tidal electricity generating system.
As the incoming tide raises the sea level against the structure, the water is forced through the structure turning the turbine and the generator producing electricity.
As the tide goes out due to the sea level reducing, the water runs through the structure in the opposite direction, again turning the turbine and generator.
The Wave system on the right uses air pressure [increasing and decreasing] to push and pull a piston that is connected to the generator. The mechanical force is transferred into electrical energy.
This is an alternative wave system.
This long, hinged tube (about the size of 5 railway carriages) bobs up and down in the waves, as the hinges bend they pump hydraulic fluid which drives generators.
In summary, with the exception of the geothermal system, the sustainable energy production technologies discussed have no cost on the energy that drives them, air/wind, tidal and wave power. The systems that are used in homes and other buildings cost more per unit of electricity than fossil fuel systems. The set up costs or capital outlay needed is initially high however, this will reduce as the technology improves. Finally, the wind turbines are viewed as items that spoil the visible environment.