Wednesday, 11 July 2012

"Why Solar is not the way forward"

Chris has forwarded this for discussion:  July 2012.

I recently received this post from a correspondent that installed pv solar panels at the same time I did. I don't necessarily agree with him but it's worth a read. 
Maintaining huge ocean based installations may be rather costly I suspect.  Tidal surge power is certainly an obvious renewable energy source that should be tapped. But the beauty of PV Solar, however inefficient is that it directly links a household to the mental construct of energy saving, you wait for the sun before using power where you can, you try and use less.  Also, the future is in solar buildings such as Blackfriars Station as you highlighted, Link to piece. where the roof is built of solar panels, and in solar walls and building materials, rather than our 'stick it on top of the roof tiles' approach...
Solar panels are great for those who had them installed last year. However this is because of the huge level of subsidy.
The government has identified 8 possible areas around the coast which could each take up to 200 wind turbines (WT) each .
Close to us, there is a proposed area to the west of the Needles and one off the Brighton coast. The latest generation of WT (wind turbines) come as 3mw, 5mw and even 7mw. Offshore a WT will produce 30% of its stated output as an average. This means that a 5mw WT will produce an average of 1.5mw at all times. If one assumes that the average house uses 6mw a year then in just 4 hours the WT produces enough electricity for a year’s consumption for one house. One WT will power 2190 houses and a farm of 200 will power 438,000 homes.
Compare this to solar. A 4kw system will produce around 11kw/day on average (this is being generous). Annually it will produce 2/3rds of the demand by a house (4Mw out of 6Mw). The efficiency is dire because the rating of the system is 4kw giving 96kw/day max. However the efficiency is only just over 11% in the best case scenario.
Turning to the costs, a 3mw WT will produce electricity for 6p/kwh, a 5mw WT will produce electricity for 5p/kwh, and a 7mw WT will produce electricity for 4p/kwh. These figures assume a 25 year maintenance free installation offshore. They include taking the electricity onshore to be connected to the grid and a minimum of 100 WT’s installed together. A 7mw WT will produce 2100kw on average. If you sell every kwh for 4p then the WT will earn £84 every hour or £738k/year. A 3mw WT will produce electricity at 50% extra cost mainly because of the high offshore installation costs. The energy extractable from the wind is directly proportional to the swept area (ie the size of the turbine blades). 7mw WT have blades are just over 80 metres each and the turbine has a rotor diameter of 164 metres. They are huge, but then so is the cost and the energy production. One 7mw WT will produce more electricity than 4500 4kw solar panel installations.

Solar panels produce electricity at significantly higher cost. How can the government justify payments of over 40p/unit when a WT can do the same environmental job for less than10% of the money? This subsidy will have to be paid by all of us for the next 25 years.

The future

Both WT and Solar have a limited and a small role to play. We need a predictable and a green mainstay of energy production. Tidal power is predictable and runs for 20 hours out of 24. Although more expensive than WT’s per kwh, we have to go down this route. This is because we all expect to use electricity on demand. Appliances are all made to run on 230/240v. When demand goes up, voltage drops. Unfortunately the Grid only has 10volts to play with or 1/24th. A variation of less than 5% clearly shows the limits of Solar and WT.
The Bristol Channel has the second highest tidal variation in the world of over 14 metres. By creating a “lake” from the south of Weston to the south of Cardiff, one will certainly alter the landscape and characteristics of the area forever. But the environmental impacts are known to be mixed, so it is not all bad news. The overall energy produced would be a minimum of 5% of the national demand and could be as high as 7%. These figures mostly depend on the scheme chosen. Multiple other smaller projects are possible.

I am not against any form of green energy. It must however either bring a guaranteed supply or be cheap. Solar is neither.

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