Lights to go out on Sark ? ARCHIVE NEWS

[adam2]

There is held to be a risk of an island wide blackout.
Sark generates its own electricity, almost entirely from diesel fuel supplied by ferry, this results in very expensive electricity, 66 pence a unit or about four times the UK mainland prices.

The electricity company have been told to reduce prices, this they have declined to do on the grounds that they would lose money.
As a result they might close down.

I suspect that some last minute deal will be done and that the lights wont actually go out, but it COULD happen.

Shows the folly of being almost totally reliant on diesel fuel, from both price and availability concerns.

Sounds as though they need some renewables, and possibly grid connected battery storage.
Grid connected batteries don't NORMALLY make sense, but such a small system is a special case and batteries can make sense via fuel saving.

Link to news report
https://www.bbc.co.uk/news/world-europe ... y-46342492

[clv101]

500 people on an island, currently 66 pence per kWh?

That's just daft - a decade ago, when government subsidies were still good (were they available on Sark?), the island could have deployed a couple of ~100kW wind turbines and ~100kW of PV. Couple that with a few thousand kWh of battery storage and the existing diesel generator for occasional/intermittent use.

I guess Sark is pretty much run by Barclay brothers - no surprise they're in such a mess.

BBC article makes no mention of renewables, either at the personal or island scale.

[adam2]

IIRC, Sark is not owned by the Barclay brothers, they own a different and nearby island.

Sark power station has 4 generators, either of the two larger units can supply the entire load, or the two smaller units combined can meet the load.

Such a system has the merits of simplicity and can run unattended. It is not particularly efficient.
Adding significant wind or solar to such a small system is challenging since at times of low load the renewable generation may exceed the load.
The diesel generator will then trip on reverse power, quickly followed by all the grid tied inverters shutting down due to loss of grid connection.

A fundamental re-design would be needed, not simply adding renewables to a small system not designed for such.

[BritDownUnder]

I think the Barclays own an offshore island to Sark called Breqhou - Wikipedia gives details on the legal status of it. Whether they run Sark is anyone's guess. I suspect they don't give a hoot about a power plant on another island that they don't own - something that is understandable. They seem to be experts in running offshore funds that don't pay taxes to HMRC.

From memory diesels don't like running at low load due to glazing of pistons whatever that is. That reason and redundancy means that there is rarely only one generator in a small power grid.

For an example of a slightly larger island with three times the population that is attempting to run a renewable power grid look no further than King Island near to Tasmania.

See the King Island Power Plant website for live updates on the relative share of solar, wind and diesel.

[kenneal - lagger]

One of the Danish islands runs on renewables alone and a number of the Scottish islands are moving in this direct. North Uist has a share offer out now for their Community Wind Project. Application forms to invest can be downloaded from here. I have no interest in this apart from possibly investing myself.

[adam2]

Indeed, Sark COULD be powered largely or entirely from renewables, but this would involve substantial re-design, not simply adding renewables to the existing system.

A large battery and a very large inverter would seem to be required.

A relatively high voltage battery, perhaps about 500 volts at say 2000 AH, or about 500 KWH useable, and a large inverter able to supply 300kw.

Charge the battery from a couple of large wind turbines, and perhaps 100kw of PV.

That would supply the entire island outside of the peak hours.

Add 4 new high efficiency diesel generators each of say 250 Kw capacity.
Any three of these could supply the entire load, leaving one as a spare for breakdowns.

A fairly clever computerised control system would start one generator under the following conditions.
Load is over 250KW.
Battery state of charge is below say 70%
Battery discharge current is excessive.

It would shut down the running engine under the following conditions.
Total load below 200KW.
Load on engine less than 50Kw.
Battery 90% full.
Net charging current available, and battery at least 60% full.

A second engine would be started when the load justified this.

If the single running engine trips, the battery and inverter should be able to meet the entire load for say 30 seconds to allow for starting a second engine.

[adam2]

A deal has been done and the lights are not expected to go out.
It remains to be seen if renewables will be used, or if this is simply a change of ownership but otherwise BAU.

[clv101]

At 66p/kWh, plus this ongoing uncertainty of supply, I'm surprised many of the houses aren't already 'off-grid'.

[adam2]

Generating your own electricity from diesel burning generators can easily cost 66 pence a unit.
A liter of diesel in a large modern generator can produce 4Kwh, or about 2Kwh for a small set under part load.

With diesel at 60 pence a liter, that is 30 pence a unit just for fuel.

Now consider the purchase cost of two generators and the cost of maintenance, and eventual replacement of the generators.
And battery storage for when the engine is not running, and battery replacements.

If I lived on Sark, I would consider diesel generators only if the waste heat could be used for space or water heating.

Or what about PV?
Getting cheaper, but still a large outlay, and electricity cycled through a battery costs about 25 pence a unit for battery depreciation.

A 5Kw PV array would cost about £5,000 just for the modules, or perhaps £10,000 including installation, cables, and controls.
Battery storage is about £500 a Kwh, say about another £10,000 for 20KWH.
If the battery lasts 10 years, the cost is £1,000 a year.
If the rest of the installation lasts for 40 years, that is another £250 a year.

Even at 66 pence a unit, you can buy a fair bit of electricity for £1,250 a year.

If I lived there, I would probably content myself with a small 12 volt only system for lighting, radio, small TV, laptop, and maybe a high efficiency DC fridge. 500watts of PV and a 12 volt battery of a few hundred AH. No inverter.

[adam2]

Worth re visiting this old thread to observe that electricity on Sark is now not much more expensive than non domestic UK mainland prices.

Sark price about 70 pence.
Mainland UK price, capped about 30 pence.
Mainland price, uncapped about 60 pence.

Expected UK prices for this winter, capped 50 pence.
Uncapped, 70 pence.

The once very expensive diesel generation on Sark is now becoming competitive with mainland prices that are linked to the natural gas price.

If I was in charge of Sark electricity, I would hope to use the waste heat heat from the power station for space heating and domestic hot water. Pumping hot water for significant distances sounds unlikely, but for the pub and households near the power station might be viable.

[adam2]

It looks as though renewable energy will belatedly be used on Sark.
https://www.bbc.co.uk/news/world-europe ... y-63154668