HILARY Broughton (Wind turbine threat to our community, Letters, March 12) draws attention to some of the problems associated with wind generation: the visual intrusion, the effects on some people of the low frequency sound and vibration, the dangers to birds, and how it is paid for.

However, I would like to clarify some of her remarks.

When the wind is blowing, we use the electricity generated in preference to that generated by fossil fuel power stations.Thus for every unit of electricity generated by wind, a unit of electricity generated from fossil fuels is displaced, along with its attendant CO2 emissions.

This, after all, is one of the main reasons for moving over to renewables.

The amount of CO2 emitted during the lifetime of the system is also relevant. Such a life cycle analysis covers the construction, including resource extraction, the operation, and the decommissioning.

The results of these studies show wind typically emits 12g per kWh of electricity generated, gas between 450g and 650g, coal 980g to 1000g, and nuclear up to 21g.

The grid system has to balance, second by second, the supply of electricity with the demand for it. Historically, this has meant that supply has to match a fluctuating, yet reasonably predictable, demand – think of the surge in power at the end of the 2011 royal wedding when people switched on kettles.

Now, with an increasing renewable component, a problem facing the grid is how to match demand with a fluctuating, yet reasonably predictable supply. In principle, this is the same problem, yet the scale of the challenge increases as the proportion of renewables increases.

Everybody involved in contributing to decisions about where renewable installations are sited will need a clear view of the issues, both pros and cons.

CHRIS SPENCER Fownhope