Feed-in Tariffs - An explanation

Feed in Tariffs are generally described as those fees that the microgenerator - who is normally the power supplier's customer - will be paid when they can show that they are putting power back into the grid.

At the moment these are low and reflect an amount such that the power company at least breaks even but can identify the microgenerator's electricity as contributing to their renewable supplies. So, the power company looks greener, potentially at the expense of the microgenerator who has made the initial capital investment.

A microgenerator can also claim payment for ROC's. Put simply, these are Renewable Obligation Certificates which are paid at the rate of about £40 per 1000 units of electricity or effectively per Tonne of CO2 that has not been emitted in the generation of electricity. More recently, Scottish and Southern Electricity have introduced an 18p /kWh feed in tariff. This is based on exported electricity and the nominal value of the ROC combined in one tariff.

In Germany, feed in tariffs for microgenerated exported electricity, are in the order of 45p per unit. This additional payment has transformed the renewable energy market (microgeneration) in Germany which is many times larger and far more advanced than that in the UK.

How does electricity exporting work in practice.

The first requirement is to have an acceptable means of generating locally, this usually means a grid connected solar PV (Photovoltaic) system. Many of these solar electric systems that have been professionally installed over the last few years and have been part funded through grants such as clear skies will most certainly be grid connected.

The almost standard system where solar PV has been installed as above will include an inverter such as the "sunny boy" which needs a 230volt mains connection to function.

A Simple Description: The Sunny boy is setup so that it detects the voltage coming in from the grid and when being charged up by the sun, puts that power back into the local mains circuit at a slightly higher voltage. Thus, the solar PV generated energy / electricity is used in preference to the mains electricity. A fairly basic understanding of V (volts) over I (amps) equals R (resistance) can help.

Where the property is using less electricity than the Solar Panels are generating, the electricity is effectively pushed out into the wider grid. In very simple terms, this would cause the consumers meter (old fashioned meters with the spinning disk) to run backwards. Modern digital meters do not show this exported electricity.

To measure exported electricity, it is necessary to install an export meter which of course indicates the amount in units of electriity that is being put back into the grid.

The export meter shown to the right is an Elster A1700, which is located at the point where the mains eneters the property and measures the actual units being exported. This works alongside the Elster A100 which is positioned at the point where the solar generated electricity is fed into the household supply, usually connected through a consumer unit.

How much electricity is likely to be exported?

My Elster shows 2440.07 kWh over a period of about 2 years. Which at the nominal 8.5p that I am paid by Eon represents a little over £200.

There was a recent project EAMA Energy that was run through 2005 to 2007 that monitored the levels of energy generated, used locally and exported for a range of solar, wind and hydro systems.

The results can be seen by going to the EAMA website which generally show that during the summer months, there was a noticable and consistent amount of electricity generated and exported to the national grid on a daily basis.

Considering the results, it shows a consistent and predictable amount of energy being generated and exported by Solar PV systems. Wind and microCHP came a poor second.

Feed in tariffs: Links

Good Energy who have a range of feed-in tariffs including one aimed at the Commercial customer.

Wikipedia : Renewable Energy World : Friends of the Earth