Rain Powered Transport

When we show the b-bug prototype our sign says “powered by rain”.  This tongue-in-cheek claim is intended to generate intrigue, and although we have had some punters who think we have invented a water-powered vehicle, what we’re actually talking about is hydro-electricity, and in particular locally generated “micro hydro”.

Electric cars have their naysayers whose motives may be questionable but whose arguments are valid.  It is true that today’s electric cars are powered by an electricity generation system that is largely dependent on burning fossil fuel.  So, the argument goes, electric cars are just as bad as normal cars in terms of fossil fuel depletion (if you’re worried about peak oil) and/or in terms of carbon emissions (if you’re worried about climate change).  That isn’t quite true, because electric cars use energy much more efficiently per passenger kilometre – particularly in towns – and a growing proportion of our electricity supply does come from renewable sources such as hydro-electricity.

We buy our electricity from Good Energy, who get all their power from renewable resources.  That doesn’t, of course, mean that when there is no wind, water or sun that our power goes off – our electricity is subject to the same grid mix as everyone else – but it does mean that our slightly higher electricity bill is in a small way encouraging investment in renewable generation.  And it means that we can claim that our electric vehicles – we have a couple of electric bikes, too – are not depleting fossil fuel reserves or adding to overall carbon emissions.

The reality is that there are currently so few electric cars in the UK that all of them could be quite comfortably powered from current renewable capacity. Since they are in the main battery operated, this could even be more literally true than it is today: electric cars could, with a “smart grid”, only take electricity when enough is being renewably produced and even (it is sometimes proposed) be prepared to put it back at other times.   In this interesting future scenario – apparently being taken seriously in Israel – a critical mass of electric cars using their batteries to store energy for their own use and as a general buffer for other users against the inconsistency of renewable energy supply.

This particular debate is made more interesting for us in our capacity as directors of Talybont Energy, a community company that owns and operates a 33kW turbine above the village of Talybont-on-Usk in the Brecon Beacons.  33kW – which is its winter output – provides enough electricity for 60 to 70 average homes, or to keep over 150 B-Bugs on the road, assuming that each of them uses about 5kWh to travel 30 miles every day.

This opens up a new USP (“unique selling proposition”) for the Brecon Beacons as a tourist attraction.  Our visitors come here to enjoy local products – fresh air, scenery, active leisure attractions and pursuits, locally grown food and locally brewed beer.   And now we can add to that locally produced energy.  We have been trying, with mixed success, to promote the idea of our locally produced energy as having a distinct feel to it that is unavailable anywhere else.  If we were French, we would insist on the government branding and protecting Brecon Beacons Electricity to prevent rival (or worse still, “foreign”) producers pretending to offer anything equivalent.  More seriously, we think that as more people become “environmentally sensitised”, this is the kind of thing that will start to matter to the more discerning visitor.  Already, there is a “market” for so-called eco-destinations where the holiday maker can be assured that the environmental impact of their vacation is minimised.

The Brecon Beacons has large hydro-electric potential which The Green Valleys organisation is working hard to realise.  And while we need to be realistic about how much hydro-electric energy we can extract from this wet upland area, it’s worth considering how far hydro-electricity could go to meeting the transport requirements of the people living in, working in, or visiting the area.

Upland areas are better for hydro because (a) there is more rain and (b) once it hits the ground it has further to fall to the sea.  The upper limit on the hydro-electric energy available from a given land area is a function of the average rainfall multiplied by the average altitude.  For the UK as a whole, the potential energy from rainfall is about 7kWh per day per person, but practically speaking, the most we could ever extract (and even then with dire environmental consequences like dams and constricted river flows) is about 1.5kWh per person per day over the whole of the UK.

But even during the visitor season, the Brecon Beacons is much more sparsely populated than the UK as a whole, and has more than its fair share of rainfall and altitude.  Professor David MacKay calculates that for upland areas like ours the raw potential energy of rainfall amounts to about .24 Watts per square metre of catchment area.  This means the 1344 square kilometres of Brecon Beacons National Park offers a massive 322 MegaWatt of potential power, although extracting more than a tiny fraction of that would be very costly and environmentally destructive.

To see how small a fraction, the hydro potential of the 32 square kilometre Talybont Turbine catchment area is 7.5 MegaWatts but the turbine captures less than half of one percent (33kW – 0.43%) of that, even with the benefit of a large dam. So in effect, we’re capturing about 1kW per square kilometre of the hydro potential. [That's still 4 times as much per unit of area as the 3 Gorges Dam in China, the largest hydroelectric generator in the world, which produce 22.5 Gigawatts of electricity from a catchment of 1 million square kilometres, at an environmental cost which has yet to be realised].

If we could convert the hydro-electric potential of the entire Brecon Beacons National Park at, say, twice the efficiency of the Talybont Turbine then the 1344 square kilometres of park could, at 2kW per square kilometre, generate 2.6 MegaWatts.  This is enough for about 5000 average UK homes.  Professor MacKay estimates UK energy consumption for car transport at around 40kWh per person per day, so that 2.6 MW could instead meet the transport needs of 1600 people, or 5% of the resident 32000 population of the park.

With lighter, slower and more efficient electric vehicles like the b-bug, travelling an average of 30 miles a day (11,000 miles a year) at an energy cost of 5kWh per day, 2.6MW can supply the transport needs of 13,000 people. That’s about 40% of the population of the National park, which is a more impressive result, but still well short of a comprehensive solution.

The one thing we can be sure about is that hydro-electricity alone can never make the Brecon Beacons National Park, let alone the UK, carbon neutral in either domestic electricity or transport.  But used in the right way, and more sensibly, hydro can make a significant difference in areas like the Brecon Beacons National Park, even though its national impact is always likely to be marginal.

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