Data Centres and Renewable Energy Project
What about connecting to the grid?
We chose not to consider a grid connection in this study because this does not in itself answer the challenge of balancing a high, constant electricity demand with intermittent sources of supply – the problem simply moves elsewhere. We wanted first to establish the scale of the problem and the practicality of potential off-grid solutions. In each case however we did include a backup diesel generator in order to meet availability requirements.
However, in real life it is very unlikely that a data centre would be truly off the grid, so we took a qualitative look at how this could work, including scaling up from our demonstrator to a larger, commercial scale data centre.
Connecting both data centre and renewable energy generator to grid:
In this case the data centre is actually being supplied by the grid. The energy would be coming from whatever mix of fossil and renewable sources that happen to be on stream at any time, and the data centre could not claim to be powered wholly or largely by renewables unless the grid as a whole was.
- The grid operator must provide either storage or other backup capacity that is easy to bring on line. This could be hard to do in the context of a local area alone where it adds noticeably to local demand. Even our small data centre consumes the equivalent of 375 households over the year; and during the critical evening peak load period is adding about 150 households’ peak demand (2).
- Connecting a new renewable source to the grid may take some time,. In Shetland the total demand ranges from 29-50MW through the year (1), and with 5 MW of wind already in this mix, the operator is not allowing any new intermittent sources to be connected at all (3).
- If the grid has excess electricity to export out of the local area, then the energy generator would earn more revenue through Renewable Obligation Credits by selling to the grid rather than directly to the data centre even with Feed-In Tariffs. (4).
Connecting only data centre to the grid
Here the data centre is using the grid as a backup to avoid storage; the renewable energy source is not connected to the grid and so avoids the problem of access. However it introduces new challenges.
- The excess electricity generated during periods of high wind or peak tidal current would be wasted, unless some other means of converting it to a useful output were introduced. An example can be found in Orkney where a small entrepreneur is altering their hours of jam production to fit in with periods of high wind (5).
- The data centre operator would have to pay a high tariff to be guaranteed to be supplied with its needs irregularly and at short notice, even when normal domestic and commercial demand is at its peak. They would get a much better rate if they took all their energy from the grid and formed part of the base load. The bigger the data centre, the more incentive it would have to do so.
Conclusions
- If renewable energy is to be used for powering large scale data centres in areas where it is not possible or easy to export large amounts of energy, then the problem of storage will have to be solved at least at the level of the local grid.
- An area worth investigating further is whether there is an economically feasible way to combine wind turbines connected to the grid, with some amount of storage, so that the energy store only needs to cover the hours of peak loading on the grid.
References used in this page:
(1) Drew Ratter, personal communication, 2 April 2010
(2) Robertson, G, 2009: Wind-Hydrogen Community on the Isle of Lewis; MSc Thesis, University of Strathclyde
(3) Shetland News, 2009: http://www.shetland-news.co.uk/2009/November/news/SSE%20bar%20small%20turbines%20from%20Shetland%20grid.htm , accessed 20 April 2010
(4) DECC 2010: Feed-in Tariffs: Government’s Response to the Summer 2009 Consultation;Dept of Energy & Climate Change, February
(5) The Press & Journal 2010: Island producer creating a stir; http://www.pressandjournal.co.uk/Article.aspx/1692508?UserKey=, 17/04/2010, accessed 17 April