New builds - solar and wind power

[Ann Tigonie]

Getting to the point

I think you need to ask 'cost effective for who?'

If it's more cost effective for the owner to run, that doesn't mean that it'll be more cost effective for the builder to build. Modern housing is built the way that it is in part because that approach allows for standardised methods and components. A large number of UK builders have no experience of building eco-houses, don't know where to get the bits, don't have the skills available and don't want to do it because they know it'll cost them money to figure all that stuff out.

I took the circuitous route Bernie, but you've got right to the nub.

 

[Cid]

Anyone know the score on generating low amounts of energy to store in batteries, big batteries like, sure I saw this happening in Machynlleth a while back

Yeah but then you have to make the batteries, which have their own associated environmental problems...

 

[free spirit]

Anyone know the score on generating low amounts of energy to store in batteries, big batteries like, sure I saw this happening in Machynlleth a while back

erm what do you want to know?

good for off grid installations, usually when coupled with 12/24 volt lighting systems & backup generator (not essential, but you'd need to have sufficient battery storage end renewable capacity to cover you through the longest nowind / cloud periods or accept there'd be some periods of no power), you then use an invertor to step up to 230 volt ac for some mains applications, but most invertors lose 5-10% of the energy just in the conversion process.

If you're talking about pretty much trickle charging a large battery bank, you're likely to end up with that battery bank spending much of it's time during heavy usuage periods hovering around the low end of it's voltage range for long periods without a proper charge up, which ain't good for batteries as they can develop a 'memory' which basically means that even if you charge them fully they'll not hold they're charge and will rapidly return to the lower voltage state (obviously it ain't really a memory, it's todo with the batteries plates getting fucked, and I've not looked into it for 5 years so can't remember the full terminology).

anyway if you're on the grid you should be going grid connected*, or potentially working out what the base load is in your house and just getting enough to always power the base load, with any extra being diverted into your immersion heater to create hot water... essentially this way the leccy you generate should get used within your house, and you'll never be exporting to the grid so don't need to install a meter etc. not entirely sure how this actually works in practice with informing the leccy board etc. but i've got a feeling it'd be frowned on, and you'd still obviously need to use the same level of grid connect invertors etc.

*possibly unless you were already planning to rewire the entire house, but even then you're adding batteries into the equation for no particular reason IMO.

 

[free spirit]

btw I agree with backatcha's recommendation of proven turbines, they're good solid, tried and tested pieces of kit, and I understand the companies pretty sound as well.

I also share the reservations about using the windsave turbines for household use as there's loads of turbulence associated with house roof installation, and I don't really see that they've made any modifications to the design to enable the turbine to cope with this (could be wrong but I've seen no evidence and it looks like a very bogstandard bottom end design). What this means it the bearings will go fairly quickly, meaning it'll become increasingly noisy.

I was quite excited about the potential for the Swift Turbine a couple of years ago, which was supposedly designed specifically for rooftop installation, with several features to make it quieter / more able to deal with the turbulence etc. but I've not seen any reviews of it's actual performance now that it's been installed in a few places for a couple of years... anyone?

 

[Backatcha Bandit]

I'd love to see some real world actual figures relating to the 1.5kW swift - the BWEA have a page on 'case studies' relating to 'small wind', but real figures still appear illusive.

Berwickshire Housing Association - Three 1.5 kW rooftop turbines Swift wind turbines

Berwickshire Housing Association (BHA) installed Renewable Devices 'Swift' domestic wind turbines on two houses in Whitsome, and another in Ayton, Berwickshire, Scotland. BHA recognises that affordable housing is not just about the cost of rent, but also the costs of heating and running a property. By installing small scale wind on tenants' houses, BHA aims to lower tenants' fuel costs and reduce their reliance on fossil fuel based energy sources.

Director of Operations at BHA, Alastair Brown, says, "One aspect of our approach to addressing fuel poverty has been to focus on the use of renewable energy systems. These innovations provide energy saving features at a more manageable cost to tenants." BHA is hopeful that these installations will prove successful and is looking to install small scale wind at several other properties across its housing stock.

http://www.bwea.com/small/cases.html

There's a document on the BWEA site entitled 'Domestic Roof-Mounted Wind Turbines - The Current State of the Art', dated 2005, which quotes figures for the Swift stating a claimed output of 4000kWh/pa and an estimated output of 1753kWh/pa.

Trouble is, that's assuming an average windspeed of 5.5 m/s - which is a hell of an assumption for something that's supposed to be designed for the 'urban environment'.

With it now being 2007 and still no real-world figures available, one can only assume they're nothing to be proud of.

So I've emailed BHA.