Types of renewable energy

There are five types of solar energy:

i) Solar Energy: The solar Heating is the most popular renewable technology for the UK households used for water heating with the better payback than photovoltaic and it is a broad network for the established installers and provider. Over 70% of the average household’s energy is used toward heating purposes so a renewable source of free hot water can make a drastic financial impact (IPCC, 2001). The energy saving measures such as the wall insulation pays back in 1-5 years. The heating and plumbing is recognized certifications such as IPHE, CORGI or APHC guarantees about the quality plumbing and the heating expertise to install, size and the balance should be effective.

The properly sized heating system can provide up to 50-80% of all the hot water requirements throughout the year. This would result in the reduction of carbon dioxide emissions around 500kg per year.

The solar water heating is mostly used for water heating and not for generating electricity with photovoltaic. The generated electricity from photovoltaic can be fed back to the National Grid. However in some vendors who are coming up with the solution where the photovoltaic panel and the solar panel are installed side by side to provide electricity and solar heating at the same time (Johansson T B, 1993).

The solar panels are usually installed at an angle of 30 and 60 degrees at the south-facing the roof on the flat surfaces. There should be some additional space for the water cylinder if required.

ii) Photo voltaic: The Photovoltaic cells are used for the solar energy to generate electricity. PV cells are arranged on building’s roof mostly and some time on walls in panels and directly feed electricity into the building. The wind turbine provides reliable energy during winter when sun energy is less reliable (Jensen, S. G., 2004).  Recently the photovoltaic cell manufacturers are incorporating these panels into roof tiles as well. Many panels can be joined together to enhance power generation. Solar Panel can range from small; kilowatt-sized used for domestic homes to large scale power plants which feed electricity grid.

PV panels are most effectively used in remote areas where it is hard to take grid connection. PV panels and wind turbine combination are best alternative to regular grid electricity.

iii) PV for Buildings: When comparing heating systems in price PV heating systems are much more costly compared to solar heating systems? However they are more reliable when it comes to maintaining since they have no moving parts (Joskow, P. L, 1985). Another advantage is that they are water proof so they can easily be used outside and can be used as roof tiles. A typical domestic 1 kilowatt (1kW) system will cover about 10 square metres, and produce about 750kWh (units of electricity) over a year – mostly in the summer. At that level the payback on £5000+ system is very long even with the grants available, and it is not yet a viable technology where one might consider selling any excess to the grid unless one installs a large array (Krohn, S, 1999).

The cost of PV systems is falling as the efficiency of solar panels increases and the cost of manufacturing declines due to the introduction of new technologies, such as thin-film solar PV. The DTI’s Renewable Innovation Review estimated that solar PV could become cost-competitive with other forms of electricity generation by 2020–30.

iv) Heat Pump: Heat pump draws heat from ground using a collecting mechanism by making hole in ground. Only few meters down the earth crust we can find a constant temperature of range10-15 degrees in UK (Junginger, 2004). Proper utilization of this heat can result in reducing home heating load. Heat pump working mechanism is very much same as fridge but in reverse. Heat pump takes heat store in ground and brings it to interior house heat system, while fridge transfers heat from inside to outside. Certain type of heat pumps use air as source of heat extraction and are known as Air source heat pumps but their capacity in inferior to ground based heat pumps. However air source heat pumps are easily to install and operate. Input power requires to operate such heat pump is usually one kilowatt for generation of three kilowatts of heat.

Ground source heat pump cause disruption to existing building structures, but following advantages outnumbers this disadvantage:

  1. Low Operating Cost
  2. Low Maintenance Costs
  3. Durability
  4. Low Noise
  5. Reduced Emissions

A heat pump is more efficient when are installed for under floor heating system. As less temperature difference between heat source and demand increases heat pump efficiency. A radiator based system heating system usually run at 70 degree difference while a floor based system operates at 36-40 degrees.

v) Geothermal Power Generation: Geothermal is a Greek word consisting of two words Geo (means Earth) and thermo (means Heat). Thus geothermal energy is produced by heat from the earth.  Geothermal power plant takes stream directly from earth surface fracture to run turbine. Other way is by pumping boiling water from underground and separate stream on surface to run turbine. The condensed steam and other remaining process fluid are pumped back underground to get more heat (Twidell J, 2006).

vi) Bio-fuels and Bio-gas: Bio-fuels and Biogas terms are used for those fuels which are extracted from Biomass mostly from domestic, sewage and agricultural waste. Common Bio-fuels are following:

  • Bioethanol,
  • Biome thane,
  • Biobutanol and
  • Biodiesel

These fuels are utilized to produce both heat and electricity. In Brazil biofuels are used to run 90% vehicles on road. All existing petrol vehicles are able to run on a blend that contains 5% bio ethanol. Flexible fuel vehicles are able to use blends of up to 85% bio-ethanol.


  • IPCC, 2001. Climate Change 2001, Impacts Adaptations and Vulnerability. Contribution of working group 2 to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge,
  • Johansson T B, Renewable energy sources for fuels and electricity, Island Press, 1993.
  • Krohn, S. and Damborg, S., 1999. On public attitudes towards wind power. Renewable Energy, 16(1-4), p.954–960.
  • Junginger, M., de Visser, E., Faaij, A. and Claeson Colpier, U., 2004. Technological learning and cost reductions of biomass CHP combustion plants. The case of Sweden. In: 2nd World Conference on Biomass for Energy, Industry and Climate Protection, Rome, Italy.
  • Twiddle J, Renewable energy resources, 2006.

Abhinash Jena

Partner at Project Guru
Abhinash has worked in sales, branding, and marketing functions for GPS companies including MapmyIndia Navigators (www.MapmyIndia.com). In addition to writing for Knowledge Tank articles, he also writes the expert's advice for Thesis & Dissertations and Power Designs.

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