Recommended Posts

Thanks for all the replies

 

The system will be separate with PV and probably wind, powering the office with battery storage. The island grid will power the main house and I will use it to charge the batteries if local generation is low. Hopefully remove the need for a diesel generator. No problem with any DIY aspects of this.  Think I still have bits of a home built wind generator I started after being on a course at CAT in the early 90's run by Hugh Pigott.

 

Heating and DHW is still something I'm thinking about. Thanks for all the advice. I'll use the appropriate forums to follow up on this. 

 

Answering a couple of other comments further up.

 

@jamiehamy Have fun on Eigg. Where are you staying?

 

@Cpd Our friend on Eigg used to be Schellenberg's gardener back in the 90's, might be the same person,. Do you remember his name?

 

@ProDave Thanks for the offer, all help will be welcome.

 

One question has there been any bulk buys been setup before on the forum? I've heard of groups of self builders organising containers of PV direct from China as well as other material direct from manufacturers.

Share this post


Link to post
Share on other sites
5 minutes ago, tilpol said:

One question has there been any bulk buys been setup before on the forum? I've heard of groups of self builders organising containers of PV direct from China as well as other material direct from manufacturers.

If anyone is bulk buying solar PV I might well be interested.

Share this post


Link to post
Share on other sites

I will need to purchase solar PV at some point this year. I have no idea what spec yet, but definitely plan to include it in the build.

Share this post


Link to post
Share on other sites
15 hours ago, Onoff said:

I see lots of talk of battery storage as a possibility. There's another thread just started here ref Sunamp by @AndyT of Sunamp. Let's face it a Sunamp is the place to store it!

 

I've got twin SunAmps and I am delighted with them, but they definitely have a sweet spot -- that is where you need a high thermal capacity density with low heat losses.  If you are looking at onsite wind, some form of solid fuel heater such a an RMH, or infill kW from your 5kW allowance (120 kWh is a  lot of energy to use) then I would have though some some of high capacity buffer (either water or solid) at ~30°C also acting as a DHW preheat might prove more effective or at least cost-effective.

Share this post


Link to post
Share on other sites

Can you not just use the diesel genny? In the times of no solar gain it's a near perfect choice. Remote start and silenced it will top up batteries whilst also simultaneously providing waste heat to a thermal store for DHW. You can simply run this more or less on demand TBH, but I'd probably go for an LPG fired one so you can have one bottle bank and use that for cooking too. 

Space heating a passive-esque property will be child's play so I'd go for the fabric-first approach here and go all out for as near a zero energy home as is practicable. 

Great thread btw, I'm ever intrigued by the off grid solutions. 

Share this post


Link to post
Share on other sites

LPG cylinders are expensive enough here on the mainland. I expect add the transport cost and they will be eye watering on the island.

 

What do most do for heating?  I expect solid fuel to play a big part but doubt there are enough trees to provide much wood?

Share this post


Link to post
Share on other sites

I slept in the rain last night (wind changed direction and had window open).

So had a little think about this 'semi' off grid problem.

 

Could you not wire the house a bit differently so that you have light, fridge, freezer,  central heating pump/controls and maybe a couple of spare sockets on the island grid.  It may still be possible to use more than 5 kWp, but mush harder to.  I have no idea what actually happens if you do go over the 5 kWp limit.  Does it blow a fuse and need someone from the DNO to fix it, or trip out and just need a reset?  Or do they do the decent thing and charge £2 a unit.

 

The rest of the house could then be on a secondary circuit, one that is only connected to your own generation and storage.  That way you can use more power if it is being generated or has been stored.

 

As the island increases its renewable generation/storage, they may give you another, higher limit, then it is just a case of transferring a few circuits to the island grid.

 

I also think that it is worth moving away from all combustion technologies.  Shame that the island is going RE electric, then some islanders fill the local area up with smoke and fumes.  Rather defeats the object.

Edited by SteamyTea

Share this post


Link to post
Share on other sites

With a diesel / lpg genny reinforcing the island 5kw, it can literally just be used on demand. Does anyone on the island have kerosene ( light oil ) delivered / installed ? I'm sure gennys can run off kerosene. 

Share this post


Link to post
Share on other sites
9 hours ago, Nickfromwales said:

Can you not just use the diesel genny?

 

Nick, Costing the Earth did a really good podcast on Eigg's energy solution, and one of the major goals was to provide at residents with a guaranteed supply so long as they stuck to the <5 kW cap, and one of the aims was to get rid of all the noise polluting Diesel generators.

 

All houses have a 20A trip on the supply.  Basically its such a PITA losing your supply that most islanders just learn to shape their demand to avoid getting tripped.  I can't see anyone needing 120 kWh a day, so the issue isn't the overall capacity but how you proactively manage your demand to avoid the 5kW trip.   

 

Share this post


Link to post
Share on other sites
1 minute ago, TerryE said:

 

Nick, Costing the Earth did a really good podcast on Eigg's energy solution, and one of the major goals was to provide at residents with a guaranteed supply so long as they stuck to the <5 kW cap, and one of the aims was to get rid of all the noise polluting Diesel generators.

 

Ok, thanks. A bit of thought adjustment from the Welsh Neanderthal needed then :) 

Dhw is a bit of a sticking point, so even more argument to heat a whopper of a Sunamp by trickle charging it and drawing space heating and Dhw from that. A bit of disciple with use / duration of Dhw should suffice then. 

Share this post


Link to post
Share on other sites

That podcast is well worth listening to, BTW. 

  • Like 1

Share this post


Link to post
Share on other sites

The difference in noise pollution on the island from before the grid was installed is pretty significant. All you used to hear was the noise of generators where ever you went. Most folk still have them as backup but I don't think they have ever been used since the grid was installed.

 

Don't think my neighbours would be best pleased if I had a generator that was running occasionally. Even one that is "silent", the noise would travel for some distance when you have complete silence.

 

Most folk live happily with the 5KW limit (its 10KW for businesses like the shop and tea room). I believe at present the system is approaching it's limit not so much on generation but storage for any new builds on the island. I think there is moves to add more batteries. This is one reason I wanted to generate some of our own electricity as well as I like to play around with these things. I'm an electronics engineer and have worked in renewables in the past (although it was wave power).

 

There is plenty wood on the island and most folk have a wood burner. The problem up till now has been it has not been managed properly. There is now an initiative to address this  and people employed to ensure there is a sustainable supply of decent wood for heating. So BIomass is an option for hot water. Most people have a back boiler on their wood burner along with solar thermal.

Share this post


Link to post
Share on other sites
42 minutes ago, tilpol said:

Most folk live happily with the 5KW limit

I could easily live with that restriction, but it is nice to be able to get up in the middle of the night and make some tea and not have to worry about whether the water is heating or not.

43 minutes ago, tilpol said:

There is plenty wood on the island and most folk have a wood burner.

A m2 of biomass will yield around 2 kWh/year, a m2 of PV will give about 130 kWh/year.

To put that into perspective, in December, that same m2 of PV will yield over 10 kWh. Not much I grant you, but a lot better than the 'sustainable' biomass option.

 

Eigg has a total surface area of 30.5 million m2, at 0.25% efficiency (about what plants produce) and at an annual irradiation level of 90 kWh/m2, the island could produce about 7 MWh/year of biomass energy.

There is no 'sustainable' biomass plan for the island.

 

  • Like 1

Share this post


Link to post
Share on other sites
7 minutes ago, SteamyTea said:

I could easily live with that restriction, but it is nice to be able to get up in the middle of the night and make some tea and not have to worry about whether the water is heating or not.

 

s-l225.jpg.3e48f7057d09bb055cf218d14af41ebd.jpg

 

:ph34r:

  • Haha 1

Share this post


Link to post
Share on other sites
20 minutes ago, Onoff said:

 

s-l225.jpg.3e48f7057d09bb055cf218d14af41ebd.jpg

 

:ph34r:

Buy a black one and bingo, solar heated coffee. ( or tea ). 

Dragons den ?

Share this post


Link to post
Share on other sites

@tilpol, if you are doing a newbuild and can get your wall U values under 0.15, windows & doors under 1.0 and avoid the "acres of glass" that so many architects love, with a decent insulated slab, good airtightness and MVHR then you should get your space heating needs down under 2 kW even for typical Jan / Feb. 

 

The problem with a wood fire is that you will have a great dead of difficulty keeping the power output under 6 kW if you want it to run efficiently, and the burning efficiency of stacked wood isn't good; anything less than 2 years drying, terrible.   A bit of a dilemma, really. 

 

In principle the RMH approach solves this by burning at a high output for shortish period, once every few days and dumping the heat into a thermal store (typically cob) which you can then draw down as needed into the house fabric through UFH or whatever.  A quick search gave this interesting thread.  As this thread points out there are a lot of issues such as no commercially available appliances with HETAS certification.  A difficult one.

Share this post


Link to post
Share on other sites

@tilpol a 350mm jji stud wall/roof with blown cellulose will give a u value of .1, windows at .6, just had an excellent price for upvc windows, i really don't want upvc, however, other half is going 'i don't care, look at the price'! have to say it's difficult to argue.

airsource heat pump 2-3kw power input dependent on size (ecodan)

Share this post


Link to post
Share on other sites

Don't think I've ever not been able to get a cup of tea at any time of day and night when I've visited as well as getting a hot shower in the morning. It's just about adapting to the circumstances.

 

I can't speak directly for the people who currently live on the island but they have to use the resources they currently have. In general it is a low income island and not everyone has the finances to change. So for most burning wood is the only option. Therefore the initiative to try and manage the wood resources better.

 

My preference is not to use any wood and I'm in the process of trying to persuade my wife that the wood burner is not necessary.  We are used to one however as I put one in our current house about 20 years ago. We were forever having power outages in the winter and needed some form of heating we could rely on. Very few power outages these days but we still use the fire, I have a free source of wood offcuts and it still provides most of our space heating.

 

Thanks for the info on walls U-values. I had been looking at kits with a value of 0.12 but I was concerned about the costs of transportation. JJI joists does sound like an option. @Simplysimon Can you tell me your supplier?

 

 

 

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now