Around the world the definition of microgeneration can vary. Microgeneration is classified by ESB Networks as grid connected electricity generation up to a maximum rating of 11kW when connected to the three phase portion of the distribution grid (400V). The vast majority of domestic and agricultural customers are connected to the single phase portion of the distribution grid (230V) and for these customers to be classified as microgenerators the maximum technical rating permitted is 5.75kW. These ratings are in line with Irish conditions prescribed in European standard EN 50438. However ESB Networks accept applications for generators up to 6kW.
In Ireland customers with microgenerators up to the capacities outlined above can avail of a stream-lined, one page connection process (using form NC6). Customers who exceed the classification must engage in a more demanding application and connection process.
A microgenerator might use any one of the following technologies to generate electricity:
- Wind turbine
- Photovoltaic panels (also known as solar electric panels)
- Micro-hydro (scaled down version of hydro-electricity station)
- Micro-CHP (fuelled by biofuels or fossil fuels)
Two or more of the technologies may be combined to create a hybrid system. Domestic and small commercial wind microgeneration involves using a small-scale wind turbine system to harness energy from the wind. In general it is at its most competitive and cost effective in remote, exposed areas or for charging batteries on boats, caravans and holiday cabins i.e. where grid connection might be too expensive or impractical. Where wind energy is not practical PV panels might be considered. There are micro-CHP units on trial at present but not commercially available at this point. Combined Heat and Power (CHP) units are basically engines which generate electricity but the heat by-product is used to heat water. Therefore more of the energy is usefully employed and less is wasted to the atmosphere or surroundings.
With the use of an electrical control panel and an inverter the electricity generated by a microgenerator can be used to supply electricity to the home, the amount of which depends on the size of the generation installed, the demand at any given time and of course the quantity of renewable energy source available.
An EN 50438 compliant inverter is necessary for a number of reasons. One of its functions is to convert direct current (DC) to alternating current (AC) which is the type of power utensils and appliances demand i.e. 'mains' electricity. Direct current is outputted by the controller and it needs to be inverted into AC. The inverter is also necessary to synchronise the output of the turbine with the electricity being drawn from the grid to ensure the occupant sees no interruption in their supply. It is also required to ensure electricity is not sent out to the grid in the event of a power cut - while technicians work on the power lines. An EN 50438 compliant inverter is a compulsory requirement with ESB Networks.
For a Status Report on Microgeneration in Ireland at the end of 2010 please click here.
For further information on microgeneration, with an emphasis on wind power, please refer to the FAQs in this section of the website.