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Can you generate electricity from rainfall?

In the first of a new series from Business Juice we attempt to answer some scientific questions about how the future of energy could evolve.

Today we ask:

Is it possible to generate electricity from rainfall?

The last 12 months have seen an incredible amount of rainfall in the UK, in fact it’s pouring down right now, and it proved to be the wettest winter since 1766 with 435mm of rain being recorded in England and Wales up to February 24th higher than the previous record of 415 mm in 1915 and the highest since records began in 1766.

Wet indeed, but could these increasingly common wet spells be harnessed to drive power generation?

In 2008 a study was undertake using Piezoelectric devices to mimic the effect of energy generation. Piezoelectric devices contain materials where electric charge is created due to mechanical stress. In effect this is generating power, a proxy for a turbine used in traditional sources of power generation such as coal, gas and nuclear as well as in large scale water driven generation such as hydro-power.

The study found that the Piezoelectric device when encountering steady rainfall had a capacity to produce 12 milliwatts from each raindrop. This sounded positive, but this is the equivalent of generating just 0.001kWh per square meter. Barely enough to power anything of use.

Using the hydro model where water is collected in order to drive a turbine, which in turn generates energy, it is theoretically possible to use rainfall more efficiently. In a typical year (of which 2013/14 wasn’t), the UK can expect to receive just shy of a tonne of water for each meter square. An average sized house could then potentially create 3kWh of energy per year from rainfall alone. Electricity generation is a naturally inefficient process and so the usable volume of energy would be lower than this. Taking a 60% efficiency factor would mean a 185-meter square roof would generate enough energy to run a 15w light bulb for 133 hours.

For the same square meter, 60,000 times more energy is sourced from the sun than it can be from rain.

Solar energy and PV cells still look like the best option for harnessing energy production. For now rain will have to remain a seasonal annoyance.

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