# Electricity from wood heat



## Cynnergy (Apr 23, 2013)

Can anyone point me to any projects that are looking into small-scale (i.e. a few homes - 10-15 kW system) electricity generation from biomass?  I'm trying to find some renewable alternatives to the massive fuel bill for our off-grid island generator (currently 15 kW) which runs 24/7. 

Solar and wind are probably more realistic options, but it would be interesting to see if wood could be added in to the mix.


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## Ehouse (Apr 24, 2013)

Do you have battery storage and an inverter?  By adding these you could probably save a ton of $ in fuel and downsize the genset.


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## peakbagger (Apr 24, 2013)

There really isnt any proven technology out there to generate electricity from wood on a small scale. If you want to be on the "bleeding edge" there are several technologies that are not ready for prime time (and have been this way for a long time).

Wood Gas generators get a lot of press and there are firms that will sell you a system. What they dont tell you is you need to have a large supply of dry chipped wood which requires a lot of horsepower to convert trees into chips. Generally it really only makes sense to generate power if you have a use for the large amount of waste heat that the generator produces. To  generate useable power you have to think in the terms of tons of wood.

Sterling Cycle generators are intriguing but the concept has been around for 200 plus years and no one has built one that will run for any period of time.

Organic Rakine Cycle generators are sort of in production but the initical cost is high. I personally think this tech has a chance as they use the same technology that a heat pump uses.

Super Critical Carbon Dioxide generators are  similar to Organic Rankine Cycle. There are some 100 KW units in commercial stage.

Realistically the best investment is a properly designed battery storage system augmented with solar. Odds are the generator is vastly oversized most of the time and is bascially idling. By installing a large battery bank, with solar, the generator only is run when the batteries are low or every month or so to equalize the batteries. If you are on an island, you may have reliable wind and you can use that to also charge the batteries.

You may want ot get a subscription to Home Power Magazine as they have a lot of info on renewables in general, They usually have a deal on the scubscription that gives you access to back issues. One of their editors, Ian Woofeden (something like that)  lives off grid on an island in the NW and does occasion articles  on  his systems which are mostly wind.


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## Ehouse (Apr 24, 2013)

Google "New England Solar Electric" and peruse their site, Lots of good info.  They are very helpful over the phone as well.


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## EatenByLimestone (Apr 24, 2013)

Running the generator only when you need it is probably the easiest way to lower the fuel bill.  

You can also use the generator to charge batteries.  Batteries don't do well in cold weather so they may not be a very good choice since you might completely shut your cabin down when you aren't there in the winter.  A small solar system can keep the batteries charged when you aren't there.  

Figuring out ways to lower usage is probably the easiest way to lower the fuel bill.


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## Cynnergy (Apr 24, 2013)

My dad currently does all of the maintenance on the generator and he's worried that adding in a battery system would increase the maintenance costs and decrease the life of the generator with all of the stopping and starting. Personally, I think that's a false economy (use the fuel savings to hire somebody to fix it), but he's kind of old school. Do you know of any sort of calculator where I can size a system and calculate fuel savings and capital/maintenance costs?

He pointed out a short blurb in 'Canadian Biomass' magazine where they said that Pratt & Whitney had an Organic Rakine Cycle generator that was 10 kW, but I looked on their website and I can't find anything - it might have been a typo. I thought that if he was interested though that I'd try to do a bit more research.

We have lots of wood and we could buy a chipper, but I'm not sure about chipping and drying tons of chips. Could we use the waste heat from a wood gas generator to do that? How much fuel do you think we'd need to run the chipper for that many chips?


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## Ehouse (Apr 24, 2013)

After rereading your initial post I think you're talking about a whole island generator serving several homes .  Is that right?  I missed that part at first.  How far apart are the homes?  It might be cheaper (with incentives) for each home to have it's own solar/wind/generator hybrid set up.  Is there any potential for hydro on the island?


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## begreen (Apr 24, 2013)

I'm intrigued by using solar to create hydrogen as the storage medium. It's a good fuel for fuel cells and the process is relatively simple.


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## EatenByLimestone (Apr 24, 2013)

How about a small generator for normal usage and then you turn the big generator on when you need it?  I can't imagine that you need all that power, all the time.  Try completing a generator sizing worksheet.   Figure out how many lights you have on at one time and which appliances you will use together.


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## begreen (Apr 24, 2013)

That's similar to the way a sailboat is run on the ocean Matt. Run off the batteries for small loads, run the genset for larger loads like charging, desalinizing water, A/C, etc..


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## brian89gp (Apr 24, 2013)

It would probably be cheaper to directly use the heat from wood to reduce the need for electricity (heating, heat powered chillers, etc), reduce the electrical load as much as possible, then go solar/wind with a battery bank and keep the generator as backup.  Trying to generate 15kw with wood would probably be a full time job.


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## Circus (Apr 25, 2013)

Soon (not yet) it'll be easier to produce electricity. With parallel ready generators, solar and batteries using inverters you'll be able to combine small sources instead of a single large source of power.
Can't see how you could use the wood short of constantly feeding a boiler for a steam engine. Biodigesters usually collect methane from animal waste.
In a way your fortunate. You don't have a hostile money grubbing utility putting the kibosh on your schemes. Once your problems are solved we'll be envious


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## peakbagger (Apr 25, 2013)

If her father is worried about maintenance on a diesel, any of the other technologies are order of magnitude more costly intitially and will require far more time. Basically plan on someone prepping and feeding the wood full time 24 hours per day.


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## pdf27 (Apr 25, 2013)

What is the daily energy consumption? Running the generator at half load/less is liable to do it more damage than running it at full load for a couple of hours then switching it off for the rest of the day. If you've got a bit battery bank that becomes possible, and you can link in other energy sources quite easily which may mean the generator doesn't fire at all.

In terms of alternatives, wood is a pretty poor choice - you might be able to set up a gasifier and run a petrol generator off the wood gas (think all the cars with big bags on the roof from WW2), but that's about it. If you have any streams that can be used, reasonable amounts of sun or fairly consistent wind (in order of how good they are - hydro is by far the best) then they're by far the best ways to generate.


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## GaryGary (Apr 25, 2013)

Cynnergy said:


> Can anyone point me to any projects that are looking into small-scale (i.e. a few homes - 10-15 kW system) electricity generation from biomass? I'm trying to find some renewable alternatives to the massive fuel bill for our off-grid island generator (currently 15 kW) which runs 24/7.
> 
> Solar and wind are probably more realistic options, but it would be interesting to see if wood could be added in to the mix.


 

I know zero about this area, but these guys seem to be pretty active, and they offer 10 and 20KW wood gasifier generators packaged on a pallet for about $20K.
http://www.gekgasifier.com/products/product-overview

Gary


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## Cynnergy (Apr 25, 2013)

Wow thanks all!

As mentioned, the generator doesn't run anywhere near full load most of the time, but it is sized to serve everyone (if we're careful).  Most of the houses are only vacation homes now (although back in the island's heydey there was a proper community and there was even a one-room schoolhouse with 25 kids). 

Given the usage pattern, I think it makes the most sense for the full-timers (2 houses full-time plus 2 houses that are weekend homes) to get a renewable system sized for their needs.  The generator could be used full-time when there are a lot of people around and as backup for the renewable systems as mentioned above.  There are an additional 4 vacation houses hooked up to the generator, plus 6 more houses that are not hooked up but that have ancient fridges and freezers running in the old logging camp using the 'excess' generator power.  I have reno'd our cabin with minimal electricity usage in mind because I can see the way this is going in the future - but it sure has been nice to be able to run lots of power tools and shop-vacs for the past couple of months!

It's just frustrating because change does not come easily.  It's also a case of what to do first - I suppose getting a battery system makes the most sense, and then adding in renewable pieces as we go along.  There is potential for solar in the summer, possibly microhydro in the winter, and wind intermittently all year.  Maybe wood if small-scale systems ever come to commercial fruition (or if anyone wants to do a pilot project - hello P&W and Nexterra ).   That's also more things to break down though I guess, and I have no idea which one will get the most bang for the buck.  At least by getting the battery system, the link between 24/7 power and the fuel bill will be broken, and we can start to talk about things like how many freezers are running, because those will suddenly start to 'cost' money whereas now they're just using the excess power for 'free'. 

As a side note: the houses are spread out over about 1.5 km, so using waste heat from a wood power plant probably isn't feasible.  Also, I believe the fuel bill for the generator is currently running at ~$30k/year, so I imagine the payback period for whatever system we put in should be quite attractive.


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## Badfish740 (Apr 25, 2013)

Contact this guy:

http://hydrogenhouseproject.org/the-hydrogen-house.html

I know that he's built some systems for small off grid islands in the Carribean.


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## begreen (Apr 25, 2013)

Very interesting. Thanks for the link badfish. That's more what I had in mind. This guy is inspiring.


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## pdf27 (Apr 26, 2013)

Is there anything in the old fridges/freezers? If not turning them off will save you money on your fuel bill right away, even if you do nothing to the generator. It's more efficient at full load, but adding load will still require more fuel even if the efficiency goes up, so nothing is "free".

I'd strongly suggest getting a handful of cheap, secondhand electricity meters and datalogging them before you do anything else. You really need to know what your actual consumption is (ideally in each house) by time of day before you design a system. I suspect it's likely to be <2kW for most of the day (overnight, for instance), rising rapidly in the morning and evening. That suits **some** battery systems very well (be careful here - the cheaper battery systems like lead-acid are very finicky about how much you can discharge them and how many charge/discharge cycles you can have. More expensive ones like Nickel Iron are more robust but much more expensive), but you do need to know a bit about your usage patterns before you design a system.
Once you are using the diesel engine as a battery charger, rather than base load power, then assuming the battery pack is large enough the engine should be happier and need less maintenance. Fuel bills should drop, although probably not by enough to pay for the battery pack all that fast - diesel engines are relatively good at part load efficiency, and there are some losses in the batteries. As a rectal extraction, you're looking at saving maybe 10% that way, perhaps more if the overnight power demand is down to ~1kW. If you can log the generator power consumption over the course of a typical day and put the model number up on here we may be able to come up with a better number than that. However, once you've got renewables hooked in the numbers change a bit - every 10 kWh or so of renewable electricity saves you about a gallon of diesel.
Incidentally, is that $30k figure about right? Unless you're paying quite a lot for your diesel, a quick back of the envelope calculation suggests that the generator is **REALLY** inefficient. How old is it, and do you have any figures for volume of diesel used per year rather than cost? 

If you have an available stream with a reasonable amount of drop (at least 10ft, preferably several hundred in an ideal world) that plus a battery system could probably drive everything - it's surprising how little water you need for one of those. It does need to be sized to match the water supply though...
The big advantage to solar in your particular situation is that the peak generation matches the peak load on the system (the vacation houses being full), and oversizing a solar system is pretty cheap and doesn't really have any problems with it.
Wind is a little more obtrusive and does need fairly good wind speeds to work, plus requires about as much maintenance as hydro (greasing the bearings occasionally - both are much better than a diesel engine!). Again, oversizing it is fairly cheap but you will need a safe way to dump the excess power - classically an immersion heater set to pour hot water down the drain if you have too much power.


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## Ehouse (Apr 26, 2013)

If you do go to the "New England solar Electric" site, they have a small booklet titled " PV generator Hybrid system for your PV home" which gives an over view of options.


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## Ehouse (Apr 26, 2013)

I'm with pdf27 on using the generator part time.  One line of thought is not to use the genny for charging batts directly but only run it for large sustained loads and charge while it is already in use.  As an example, you could run for 2 or 3 hours in the morning and 2 or 3 in the evening.  Every one knows that is the time to do laundry,  and any other high draw uses.  You can piggy back other loads onto the same gen/run time, for example a water holding tank in each home could be filled by the well pump(s) at this time with a booster pump for the pressure tank (or perhaps gravity storage).  Each home has a battery bank and an inverter (with a DC panel box), for lite loads when the genny is down.  PV/wjnd/hydro can be added if needed.  Simply getting everyone on the same page can have significant energy savings.


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## Jags (Apr 26, 2013)

Badfish - that is a very interesting link.  Thank you.


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## Badfish740 (Apr 26, 2013)

Jags said:


> Badfish - that is a very interesting link. Thank you.


 
The guy lives about 20 minutes away from me.  I've spoken with him a few times and have been meaning to get down to see his house but haven't had the time.  He caused quite a stir when he first proposed storing all of that hydrogen on his property with the local building inspector, but luckily common sense prevailed and folks realized that tanks full of hydrogen were no more dangerous than the 500lb tanks of propane folks have on their property in that part of the state (rural area).  If I had the cash I'd definitely spring for it.  Obviously he's using conventional fuel cells, but I wonder how hydrogen would work with one of those Bloom Boxes?


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## Jags (Apr 26, 2013)

I am waiting to see the day that stuff like this is sold in "kit" form with financing options like a car.  Walk into a dealership with your energy bills in hand and bingo - you need kit 3B.  Sign here and we will have it delivered next Wednesday.


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## pdf27 (Apr 26, 2013)

pdf27 said:


> Incidentally, is that $30k figure about right? Unless you're paying quite a lot for your diesel, a quick back of the envelope calculation suggests that the generator is **REALLY** inefficient. How old is it, and do you have any figures for volume of diesel used per year rather than cost?


Just realised I got my units mixed up. Assuming about $1.30/litre, that's 23,000 litres. Diesel Gensets seem to do about 3 kWh/litre, so that's 69,000 kWh/year. 365 x 24 = 8760 hours/year, so you're averaging a 7.9 kW load. If I had to guess, I'd say you've got 3-4 hours per day of peak load or close to it (15kW), and the rest of the time at a base load of ~6kW. Over 14 houses, that's about 500W/house. Assuming that's evenly distributed (it won't be, but if the unused houses really are inefficient it might not be that bad an assumption) then the six empty houses with the ancient fridges are using ~3kW between them. If that's an accurate assumption, you're spending ~$10,000/year on diesel to keep those fridges going.

http://www.google.co.uk/url?sa=t&rc...JI0WMyiKY_ItAXHEoMgHMLA&bvm=bv.45645796,d.d2k is probably a better estimate - that suggests between 1500 and 2000 kWh/year per fridge from about 1960-1980. For 6 houses, I'll assume 6 refrigerators and 3 freezers, all at 1750 kWh/year - ~16,000 kWh/year, or about $7,000! I'd say turning those off is the very first thing to do before you even think about other energy sources.

For a PV system, I'll take a quick stab and assume that summer demand is ~20% higher than average after taking out the demand from the old fridges. 69,000 - 16,000 = 53,000 kWh/year or 145 kWh/day, so assume the summer load is ~175 kWh/day. That's a BIG solar array - getting on for 40kW if your climate is similar to Vancouver. However, it will also give you ~39,500 kWh/year (PVWatts data), worth around $17,000/year at your current diesel price. Not sure what local solar prices are like where you are, but I suspect that's a pretty rapid payback time. As a rough cut, that would leave the generator normally only running from October-March, and even in January it's only going to be running for ~6 hours/day (always assuming a suitably sized battery pack).


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## Cynnergy (Apr 26, 2013)

Wow pdf27 and Ehouse, that is AWESOME. Thank you!

Your assumptions seem to be about right too - I got my dad an Efergy meter in the UK a few years ago, and his house averages ~25kWh/day, with peaks normally under 3kW. When both of my sisters are on the island with their young kids all bets are off though - I've seen the meter logging over 7kW at Christmas with the microwave, washing machine, electric heaters, 2 fridges & a freezer going all at once plus who knows what else. I have no idea about the consumption of the other houses or the average load on the generator, but I can try to find out more this weekend when I'm up there.

$7000 for those empty fridges/freezers?!? OMG I had no idea - I'm not mechanical, and I always had been told that although they were adding a little bit of load, it wouldn't add up to much more fuel because the generator was already running all of the time anyway. Time to get some meters for sure! Or the alternative I suppose - just unplug them. Although I may not be the most popular person on the island for doing that - guess I'll need some solid numbers first.

Behaviour is a major issue to deal with - we use electricity on the island like we're connected to the grid, but it's even worse because no one wants to spend the money or have the hassle of upgrading their appliances and disposing of the old ones. Make do and mend is the mantra, but sometimes replacing something that's old (even if it works) is much better for many reasons. I guess the money spent on fuel isn't a problem for most of them, but it is for me. Plus the whole carbon footprint thing...

Right, you have inspired me to get this sorted out. There is a better way. Time to do an energy inventory and start having some serious talks with people.


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## Redbarn (Apr 26, 2013)

I've been looking into home PV systems.
However, during the research I found the following links on Island electric systems.
These are UK based but Sunny procducts are available in the USA.
Sunny products tend to be top of the line, expensive, systems but you get what you pay for.

http://www.windandsun.co.uk/case-studies/islands/horse-island.aspx
http://www.windandsun.co.uk/case-studies/islands/isle-of-eigg.aspx


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## Ehouse (Apr 27, 2013)

I'd suggest you start researching because it's not going to be simple. For example, you'll need an electrical plan that sequences load surges (such as well pumps), so everything doesn't come on at once. Learn about DC power. You may find you can create a layered system one step at a time starting with a small battery bank in each home with some DC emergency lighting and maybe a DC fridge and well pump. Then install an inverter for AC. You may find savings to be enough at this point that you don't need to go further, But you could also add solar/wind/hydro/fuel cell/ treadle/hamsterwheel etc. at any point. You'll come up with a much better system if you educate your self and your community rather than plopping down a huge wad of cash for someone else 's design and install.

I'd find some sympathetic individuals with good skill sets (plumbing, electrical, grant writing) to help set up a tentative plan, starting with your dad. Then, a community roll out with a couple o' boxes of pizza...(oops, fish fry then!). Getting everyone on board's going to be the toughest nut to crack, but with a layered approach and gradual cash outlay, you might pull it off. 

I forgot to mention that individual homes could add a small genset (with proper disconnect) if they need or want to run larger loads when the main generator is off line.

Where's your island?  sounds beautiful!


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## peakbagger (Apr 27, 2013)

This article  may be of interest, I used to work for Northern Power but they were done with the project by the time I went to work for them. Northern Power is no longer in this business but will sell you a 100 KW wind turbine which is used extensively in severe condtions like yours. but the price tag of typically $600,000 installed is probably far too priced for most. There is a offshoot of Northern that does still do off grid power but

http://www.distributedenergy.com/DE/Editorial/Sounds_a_ProblemEven_on_an_Island_1830.aspx The people who worked on the project said the prior electrcal system was a nightmare, with household cable laid in ditches with no real ground fault protection and splices just twisted together and wrapped with electrcial tape.

http://mlcalliance.org/2013/02/20/monhegan-island-gets-a-little-slice-of-the-sun/  The island is near the proposed site of a large floating wind farm so I expect they are hoping that they can get power off the turbines.

The best chance for your island is too look for a university that wants to work on a project. The system size is manageable and the location hopefully nice to visit, so some professor may be able to fund a grant to take this on as a project as its the perfect type of project that college students could work on to come up with a design.


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## pdf27 (Apr 27, 2013)

Cynnergy said:


> Wow pdf27 and Ehouse, that is AWESOME. Thank you!


No problem. Rather embarrassingly, I actually find this sort of thing fascinating.



Cynnergy said:


> Your assumptions seem to be about right too - I got my dad an Efergy meter in the UK a few years ago, and his house averages ~25kWh/day, with peaks normally under 3kW. When both of my sisters are on the island with their young kids all bets are off though - I've seen the meter logging over 7kW at Christmas with the microwave, washing machine, electric heaters, 2 fridges & a freezer going all at once plus who knows what else. I have no idea about the consumption of the other houses or the average load on the generator, but I can try to find out more this weekend when I'm up there.


25kWh/day is about 5 times my average electricity consumption (2 of us in a ~1000 Sq ft house heated with natural gas), so you can probably get that down quite a long way. At the moment you're using about 3 Jerry cans of diesel a week to power the house.
Don't worry too much about peak loads - batteries are actually quite good for short term peak loads, and just about any conceivable system will have the generator still there as a backup for just that sort of occasion.



Cynnergy said:


> $7000 for those empty fridges/freezers?!? OMG I had no idea - I'm not mechanical, and I always had been told that although they were adding a little bit of load, it wouldn't add up to much more fuel because the generator was already running all of the time anyway. Time to get some meters for sure! Or the alternative I suppose - just unplug them. Although I may not be the most popular person on the island for doing that - guess I'll need some solid numbers first.


You may be able to get agreement to turn them off for say a day or week and compare diesel use with and without them on. Bit difficult as electricity consumption will vary, but probably easier to get agreement for than just turning them off completely.

With the generator, there are two sources of torque on the drive shaft - internal resistance of the engine itself, and the electrical load on the dynamo. Since generators run at constant speed, the internal resistance of the engine is absolutely constant - the mechanical movements are identical, as is the resistance to air being pumped through the engine. That means adding load to the dynamo will directly increase the amount of fuel it needs to keep turning at the same speed.
The reason efficiency goes up at higher loads is simple - at no load you will be consuming say 5kW to keep the engine ticking over, and with no useful work the maximum possible efficiency is 0%. At full power you will be consuming the same 5kW to keep the engine turning, plus 15kW of electricity and ~25kW of extra hot exhaust gas. The efficiency has gone up to ~30%, but you're burning 40kW more diesel to do it. That means reducing the electrical load will always reduce the amount of diesel burnt. Just for diesel alone - not counting maintenance, human time, etc. you're paying something like $0.40/kWh for your electricity.
This should be a fairly convincing way of showing it - the engine burns about a litre per hour with no load on it, going up to around 10 litres per hour at full load. Increasing the load ALWAYS increases the diesel consumption. If you let me have the generator details I can probably come up with a similar curve for it.



Cynnergy said:


> Behaviour is a major issue to deal with - we use electricity on the island like we're connected to the grid, but it's even worse because no one wants to spend the money or have the hassle of upgrading their appliances and disposing of the old ones. Make do and mend is the mantra, but sometimes replacing something that's old (even if it works!) is much better for many reasons. I guess the money spent on fuel isn't a problem for most of them, but it is for me! Plus the whole carbon footprint thing...


How do people pay for their electricity? It sounds to me like you're experiencing a classic Tragedy of the Commons - the costs of reducing their electricity consumption falls to the individual, but the cost of higher electricity bills are paid by everybody.



Cynnergy said:


> Right, you have inspired me to get this sorted out. We are being ridiculous - there is a better way, technology has moved on since the 1970s. Time to do an energy inventory and start having some serious talks with people.


Sounds to me like the actual problem isn't really so much one of technology as of incentives. Nobody is paying a penalty for their own higher consumption, and indeed don't seem to be aware that they are directly paying for consumption. Realistically, if you put every house on an electricity meter plus one on the generator and share the fuel costs accordingly I suspect consumption will probably almost halve in a few months. Once you've done that you're looking at technological solutions, but when you can point to say a solar setup and tell people with confidence that it'll cost $50,000 and save $17,000/year from their electricity bill they'll start listening. If you don't have the data - and they don't believe it through not paying the bill directly - then I think you're on to a loser unless you can self-fund the whole thing.

Incidentally, if you can you might be on to a nice little earner if you offer to take over the power grid for the island and sell it to people at the rate they're currently paying. You'd have to do it per kWh rather than as a flat rate to stop them doing something stupid, but you're looking at potentially a 30%+ ROI for a solar system and something obscene like 100% for a hydro system if there is a suitable site.


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## Ehouse (Apr 27, 2013)

pdf27, you know way more about Generators than I do;  I'm seeing lots of references to variable speed units.  Honda and Yamaha for example.  Whats the scoop on these?


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## pdf27 (Apr 28, 2013)

A synchronous/fixed speed generator connects the engine to an AC generator. That means the engine HAS to turn at 50/60Hz, depending on what country you're in (or some fraction of it - you can turn it at 1500 RPM and use a four-pole generator) to give the right AC waveform. That means when you're away from their design load they're pretty inefficient, and they tend to be a bit on the big and heavy side. However, they're really cheap and simple to build - diesel engine, governor, dynamo.

A variable speed generator connects the engine to a DC generator, which then feeds an inverter to create AC power at whatever frequency you want. That has a fair few advantages - at idle, the engine can slow right down to minimum speed and hence minimum losses, you can to some extent reduce throttling losses in a petrol generator (if your ECU is smart enough), and you can use a smaller engine. The latter is the main reason manufacturers do it - a synchronous 15kW generator needs to be able to produce max power at say 1500 RPM to keep the part load losses down. A variable speed generator will have the same part load losses but be able to rev to say 3000 RPM  at max load. Everything else being equal you have an engine of half the size, which gives lower throttling and general running losses.
The downside is that until recently inverters were pretty expensive, so variable speed generators were more expensive. Now they've come down a long way in price, they're arguably cheaper to build to the same quality than a fixed speed unit (much smaller engine). The quality of the power (noise, etc.) is also liable to be higher from a decent variable speed unit.

For most situations and people, variable speed will be the most appropriate. I have some reservations about them, but they're minor ones: 
- At full load they're liable to use more fuel, so if you have a completely fixed electrical load a synchronous generator is probably more suitable. Once you start varying the load even a bit this advantage goes though.
- If you really, really need high reliability then a synchronous generator is the way to go - less to go wrong. This only really applies to places it's safety or process critical not to lose power at all though - if you really rely on generator power it's probably cheaper to buy a spare and keep it mothballed in case the generator dies, and if not don't worry about it.

Incidentally, I'm an engineer, I deal with various similar components (inverters, etc.) at work but I don't have any real hands-on experience of running generators so the above should be taken as a theoretical explanation only - I'm sure I'm missing the real life bits...


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## Circus (Apr 28, 2013)

Cynnergy said:


> the houses are spread out over about 1.5 km,​


Wonder how much line loss you have. Maybe the first thing to do is to get a couple step/up and step/down transformers. (Out of my expertise.)
First graph the load. Then you'll have an idea what's possible.


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## renewablejohn (Apr 29, 2013)

Have a look at what is happening on the Isle of Mull off the UK coast.

http://haunnblackhouse.blogspot.co.uk/2009/08/woodchip-story.html

They have a successful woodchip industry with various woodchip biomass boilers and have even got a woodchip fired thermal oil bakery on the island.  
Once you have a woodchip fired thermal oil system, producing steam and generating electricity is relatively simple.


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## renewablejohn (Apr 30, 2013)

Not saying it is cheap but the solutions are now tried and tested.

http://www.feasta.org/documents/landhousing/enliven_app10.pdf


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## pdf27 (Apr 30, 2013)

I think the real issue here is size, rather than cost - that system seems to be designed for at least a 35kW electrical load, and they seem to be averaging about 7kW with potential to drop it a bit quite easily. As I understand it, the capital cost isn't likely to go down all that much for a smaller system, and it's liable to be pretty unhappy if underused, so unless they can set up something that really needs electricity and will give that electricity an economic value then I think it's poorly suited to their specific application.

I think there is certainly potential to use something like that (gasifying boiler + Stirling engine), I just struggle to see it not being massively more expensive than a PV + Diesel genset alternative...


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## renewablejohn (Apr 30, 2013)

Well if you only want a small generator you could try one of these portable domestic engine and generators mounted on a skid.

http://www.prestonservices.co.uk/generators.html


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## pdf27 (Apr 30, 2013)

That would be the way to do it for a one-off, or building from scratch. Problem is, the only way I can see it being economical is if they already heat with wood and are willing to go for some sort of mini combined heat & power scheme. Otherwise, the fact that they already have a generator is going to give them problems with the capital costs.


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## renewablejohn (Apr 30, 2013)

Whats the problem with capital costs. Current annual spend on generator fuel $30k quote for 10kw wood generator £12k seems to me to be a no brainer if you have a source of logs and the ability to run a small steam engine. (ie  unlike larger systems which can be automatic small systems require continuous adjustment)


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## renewablejohn (Apr 30, 2013)

Cynnergy said:


> He pointed out a short blurb in 'Canadian Biomass' magazine where they said that Pratt & Whitney had an Organic Rakine Cycle generator that was 10 kW, but I looked on their website and I can't find anything - it might have been a typo. I thought that if he was interested though that I'd try to do a bit more research.


 
The reference to Pratt & Whitney and an Organic Rankine Cycle generator will be a thermal oil system manufactured by Turboden in Italy who Pratt & Whitney purchased and is now part of there energy division. Unfortunately the 10kw is a typo I think the smallest unit they do is 500kw and the largest 2MW.

http://www.turboden.eu/en/applications/applications-overview.php


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## jharkin (May 2, 2013)

Im no expert but you got a lot of good advice and Id add another vote to look into adding batteries and an inverter.  To begin with you will lower the load on the genset and over time you can incrementially add other sources like solar/wind as budget allow.

The maintenance headache sounds like the old argument against start stop systems on cars.  Paying hundreds more on extra fuel over years to avoid paying $50 for a new starter motor. 




pdf27 said:


> I That suits **some** battery systems very well (be careful here - the cheaper battery systems like lead-acid are very finicky about how much you can discharge them and how many charge/discharge cycles you can have. More expensive ones like Nickel Iron are more robust but much more expensive),


 
Lead acid is still the battery of choice in 95% of alternative energy and backup systems AFAIK.  Basically anything where weight and size is not a constraint. Even thought the energy density is low its still one of the most efficient charge/discharge chemistries (you get 90%+ of the energy back) and even when oversize to account for 40% or less average DoD (the typical cost break even point for capacity vs. cycle life) it tends to be the cheapest option.

NiFe main advantage over lead is long service life - 40 or 50 years compared to 10-20. The drawback is very low efficiency (you only get back 60% of the charging energy) and a high self discharge rate. I beleive they used to be used as Telco float batteries a lot but are not very common these days.

There is some solar outfit experimenting with using  Lithium Ion as solar storage batteries in a partnership with Tesla.  Interesting idea as LiIon has potentially the greatest charge efficiency of all but still is much more expensive and short lived (2-5yr) than Lead so I don't know how far it will get.


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## Highbeam (May 6, 2013)

What a great thread buried over here in the green forum. Sorry I'm so late so my thoughts may repeat those above. I am a utility engineer and part of my business is figuring out how and how much to bill for service.

You have a situation where it is human nature for each resident to abuse the system. They will be wasteful since there is no direct relationship between consumption and cost. Worse yet, if they think the bill is high they will purposely overuse to "get their money's worth". The only way for this system to work is to meter each service. The meters will reduce consumption overall and encourage folks to conserve. In addition to metered consumption charges you will have a base rate where the customer pays even if they use nothing, because they could have used something and you had to be ready.

A lot of the advice has been for off-grid houses and individual solutions. Well, you're running a small utility here. There are rules and methods. What if some yahoo decided he had to have some sort of machine to support his life and moved to his cabin? You would not interrupt power or he dies. What sort of obligation do you have to provide this power? What legal ramifications if the power goes out or if you tell the cabins to get their own?

Doing it right means meters. Only then can you know your electricity demands. The folks that live there part time are getting a smoking deal. You have to pay for and keep up equipment capable of handling their needs year round while they only demand it and pay for it while they live there in the summer. This means you will have a base rate and a consumption charge.

Honestly, I would break up the system and let everyone take care of their own intermittent and variable needs. I can't believe you've been wasting so much energy for so long running a 15kw set 24/7.


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## begreen (May 6, 2013)

Tidal power video here shows progress in UK.  
http://www.businessweek.com/videos/2013-05-02/tidal-flows-the-oceans-energy-producing-potential


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## Bad Wolf (May 13, 2013)

http://victorygasifier.com/


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## Jags (May 13, 2013)

Bad Wolf said:


> http://victorygasifier.com/


 
They really need a better PR program.  Statements like this:
*Leave Lemmingville and live like James Bond… Disruptive Top Secret technology gives ordinary men “Super Spy-like” powers.*

Will make some people automatically classify these folks a nutters.


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## Highbeam (May 13, 2013)

Bad Wolf said:


> http://victorygasifier.com/


 

Wow, quite a site to stroll around on. Lot's of crap like that. "space age" and "fellas".


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## Corey (May 13, 2013)

They do have a lot of data, but also a good point.  You are probably much better off getting low grade heat as a byproduct from high grade electricity generation than trying to generate high grade electricity from low grade heat.


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## renewablejohn (May 20, 2013)

Low grade heat upto 230C is ideal for use with thermal oil. Conversion from hot thermal oil to conventional steam is straightforward and very safe.


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