Small Wind/PV Systems

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Potemkin Villager
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Small Wind/PV Systems

Post by Potemkin Villager »

Some interesting case studies of island wind/pv systems, some with impressively large battery storage systems.

http://www.windandsun.co.uk/case-studie ... EilgZP7Tv0

I was particularly interested in the Isle of Muck having designed a system that never got completed. I remember talking to the very enthusiastic young SSE engineers who subsequently installed the (very expensive) Vergnet turbine system in 2000.

According to the case study "Unfortunately, although this scheme had been well maintained, it had regularly encountered problems with reliability and output - so consistently required a high level of manual intervention. By 2011 both wind turbines had become inoperable due to problems with the batteries, inverters and chargers."

I wonder if the current system will fare better?
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adam2
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Re: Small Wind/PV Systems

Post by adam2 »

Medium sized wind turbines do not seem to have a good record of reliability.
The very large machines used on wind farms seem reliable. As do the small Rutland turbines.

Power inverters have improved in recent years, but are still not the simple and trouble free appliances that one might hope for.

Lead acid batteries should last at least ten years if of good qaulity and not abused.

I would be interested to know, in more detail, as to what went wrong in the community sized scheme refered to.
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Re: Small Wind/PV Systems

Post by clv101 »

An organisation I'm involved with installed a 700MW turbine about a year ago, it's impressive how much maintenance it needs. Lots of visits from the manufacturer/contractors, there have been several minor faults related to sensors, or even doors not closing properly etc. At the end of the day it's a million quids worth of complex electronics and mechanical engineering.

I've long been a fan of small scale solar over small scale wind... I'm tempted to prefer the reliability of large solar over large wind! But large scale wind's low cost is overwhelmingly attractive.
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Re: Small Wind/PV Systems

Post by kenneal - lagger »

Who manufactured the wind turbine, Chris?
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Re: Small Wind/PV Systems

Post by clv101 »

EWT, modern, direct drive model.
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Re: Small Wind/PV Systems

Post by kenneal - lagger »

At least it can't be blamed on British manufacturing then!
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Re: Small Wind/PV Systems

Post by Potemkin Villager »

adam2 wrote: Wed Mar 10, 2021 2:44 pm
I would be interested to know, in more detail, as to what went wrong in the community sized scheme refered to.
I will try and find out more. I don't know how much might be due to the overall reliability of the components and system
as built and/or shortcomings in the maintenance regime. Often one individual local volunteer, with minimal training, gets lumbered with
looking after these system.

Their enthusiasm can wane quickly if they are taken for granted and underwhelmed by the degree of customer support. Whilst probably being a very competent "handy man" they may get way out of their depth in diagnosing where problems have arisen and possibly might make adjustments to relay settings etc without appreciating they may be making matters worse rather than better.
Last edited by Potemkin Villager on Wed Mar 10, 2021 7:52 pm, edited 1 time in total.
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Re: Small Wind/PV Systems

Post by Potemkin Villager »

clv101 wrote: Wed Mar 10, 2021 3:51 pm ..... installed a 700MW turbine about a year ago.......
Some beast that!
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Re: Small Wind/PV Systems

Post by BritDownUnder »

When I worked on the GE wind project in Australia the issues were mainly with parts relating to the control system, in particular a part known as the 'converter' which there was one for each blade, placed in the hub, which had the job of controlling a small DC motor that would alter the pitch of the blades, in the event of an emergency shutdown, to a neutral or furled position so the blades would no longer generate power in the wind.

The problems with the turbines seem to relate to accessories rather than the turbines but the inverter seems interesting. A quick google search of the company it seems that, although French, this company does a lot of business in more remote areas of developing countries.

I would guess that the Muck system was introduced in 2000 and there was a bit of 'early adopter' syndrome to the project. Maybe bad design as well. Perhaps too many cycles for the lead acid batteries or too much deep discharging. Good to see they have got a mix with some solar in the new system. Look at the King Island system off Tasmania for comparison.
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Re: Small Wind/PV Systems

Post by Potemkin Villager »

Yes King Island looks interesting and seems to suggest 60% renewable grid supply is
a practical limit with reasonably sized battery stores and flywheels, but at very high prices (7,000 dollar/kW).

https://euanmearns.com/a-first-look-at- ... n-project/

The article concludes with a sentiment I totally agree with :-

" It’s clear that the low prices for intermittent wind and solar bid at recent capacity auctions apply only when the local grid assumes all responsibility for balancing and grid stability. When wind and solar have to stand on their own feet it’s a different ball game."

https://hybridpowersystems.org/crete201 ... mitris.pdf

I am currently reading this article on wind energy in Crete, written in occasionally hilarious Greek English. I wonder how the
combination of extreme renewable development fever on the island, and the social push back against it, along with the imminent interconnection with the mainland will impact on the proposed pumped storage schemes?
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Re: Small Wind/PV Systems

Post by clv101 »

I've lived off-grid for the last 2.5 years. The key thing, the most important thing, is to organise your life and technology around the intermittency. Just making small operational changes mitigates the need for many thousands of pounds of batteries or ludicrously dimensioned systems. Our available energy can range from 0.5 kWh to ~50kWh, worst days are just 1% of best days.

For example, I never bake bread or make pizza after dark. In the winter we tend to have our main meal at lunchtime with something lighter/cold/leftovers for dinner. Stuff with thermal mass like the freezer and fridge are on timers so they are off from say 1am-7am, saving additional battery cycling. I make a lot of use of battery stuff - vast majority of my power tools are 18V, if I'm planning to do a lot of work in mid-winter or a particularly dark day, or after dark I make sure all batteries are fully charged over the previous few days. Almost all IT use is laptops/phone, typically used after dark after charging during the day. Also have decent corded electric lawn power, strimmer etc

Relying on renewables AND expecting completely unencumbered demand is unrealistic - you must be adaptable.
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Re: Small Wind/PV Systems

Post by adam2 »

For an owner installed and operated system that supplies only the home of the owner, then I agree entirely. Life has to be planned around the available energy, and minimising the energy cycled through the battery.

However the O/P refers to a COMMUNITY system, these should have the advantage of scale, but also have a very significant drawback in that electricity supplied "by the utility" tends to be used freely without regard to the full circumstances regarding renewable input and battery state of charge. Even if "the utility" is small and community owned.

In my view, such systems need smart metering at the point of use, with at least three different rates.
LOW--------------5 p a unit, only applicable when power availability significantly exceeds the demand.
STANDARD------15p a unit, when supply and demand are broadly in line.
HIGH-------------60 p a unit, when demand is significantly exceeding renewable input which can only be met by significant battery discharge, or perhaps by diesel generation.

Rates are only indicative. The high rate should contribute to battery replacement or diesel fuel purchase.
The medium rate, should pay the interest on the capital cost, and contribute to a "sinking fund" for eventual renewal of the longer lasting assets.
The low rate, should be a modest contribution to the fixed costs of providing the supply, maintenance of equipment, wages etc.
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Re: Small Wind/PV Systems

Post by Potemkin Villager »

The original Fair Isle & Foula had just such a scheme. The consumer units were primitive smart meters
with 3 off analogue kWh meters controlled by frequency sensitive relays which switched the voltage sensing coils.
One meter was for diesel, the second for wind and the third for dump load into immersion heaters and electric
storage heaters.

Peoples expectations of what renewable energy might deliver is dependent on their historic experience. Consider the following account of the experience of folk living on Muck.

https://books.google.ie/books?id=iJ28BQ ... le&f=false
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Re: Small Wind/PV Systems

Post by emordnilap »

clv101 wrote: Fri Mar 12, 2021 10:48 pmyou must be adaptable.
99% of people in the minority world either can't be or won't be.

Take a simple thing such as solar hot water: use it when you have it. Plan around it.

That's a far-out stinky hippy massive no-no.
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Re: Small Wind/PV Systems

Post by adam2 »

Solar hot water may used almost whenever desired provided that a very large and very well insulated hot water tank is installed. This applies to both direct thermal systems and to immersion heaters powered from PV modules.
With PV water heating, the water may be heated to almost boiling point, which does in effect increase the storage capacity. An automatic mixing valve is most important to avoid scalding.

Storing hot water is easier than storing electricity.
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