## Monday, January 7, 2008

### How much hydro does it take to "power Glasgow"?

Whenever a renewable power facility is described they always say how many 'homes' it will power. Today's news says The 100MW Glendoe Hydro Scheme will be able to power around 250,000 homes – equivalent to a city the size of Glasgow.

I think this 'homes' description is really misleading, because I bet people confuse 'powering all the homes in Glasgow' with 'powering all Glasgow's electricity' or even 'powering all Glasgow's energy'.

Let's do a simple calculation.

The average expected power from Glendoe is 180 GWh per year [source]. Now
if we take 180 GWh per year and share it between a Glasgow of people
(616,000 people), we get 0.8 kWh/d per person.

OK; what is the average electricity consumption per person (including all forms of electricity, not just domestic)? Answer: 16 kWh/d per person. So Glendoe actually provides 5% of the electricity consumption of Glasgow.

So if people get the impression from the press releases that Glendoe will power Glasgow, they have been misled by a factor of twenty!

This is a bigger factor than the normal factor by which people are usually misled. The statement
that Glendoe (180 GWh/y) would power 250,000 homes implies that each 'home' uses just 720 kWh per year. But the normal assumption in press releases about wind or tide is to assume the average home uses 4000 kWh/y or 4700 kWh/y. What's going on? The ratio between 720 kWh and 4000 kWh (18%) is suspiciously similar to the ratio between the average power production of Glendoe (180 GWh/y) and its capacity (100 MW is equivalent to 877 GWh/y). Methinks that someone at Scottish and Southern must have screwed up (or deliberately misled the public) by pretending that Glendoe will produce 100MW 100% of the the time, whereas in fact it will have an average load factor of 20%.