Renewables to replace our diesel genny

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kenneal - lagger
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Renewables to replace our diesel genny

Post by kenneal - lagger »

I've been planning a new barn/shed for wintering our animals and that would give us a roof where I could put about 20kWp of PV on a ridged roof or 40kWp if it was monopitched from north to south. This, combined with a wind turbine or say 6 to 10kW, would enable us to run on renewables most of the time with the generators as a backup. I was also thinking about replacing our car with a small plug in electric car and possibly combining that with the energy storage. We have 1350Ahrs of batteries at the moment which are run to 50% Depth of Discharge and I was thinking of doubling or even trebling that. The car doesn't get that much usage, probably ten miles a day on average with some days at about 70 miles and the occasional 220 mile round trip to Wales or 140 mile round trip to the beach.

My daughter, son-in-law and family live with us and they have two cars, one of which is a small run which they use mostly and could be replaced with an small electric car when the time comes for its replacement. That car probably does twice the mileage of ours so it is still not a massive usage.

Any thoughts would be appreciated.
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anotherexlurker
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Re: Renewables to replace our diesel genny

Post by anotherexlurker »

The points I would consider

What are your current and expected usage patterns (in kWh) in particular the time of day and time of year and how does that compare to the likely panel output at those times (height of the sun and height of anything that could/would cause shading needs to be taken into account). The closer the match the smaller the battery storage required and vice versa.

Which electric cars can you actually use the the battery pack as house storage (obviously anything can be jerry-rigged , but that would effect warranties). We have to assume that eventually all/most electric cars will be capable of 2 way flows as it makes so much sense, but that probably requires forward thinking sensible politicians (there always seems to be a world shortage of those!!) to legislate on a standard (that is hopefully decided upon by actual engineers rather than civil servants).

If its not possible to use the large kWh battery pack of the electric car/cars as part of the storage and you can't export to the grid and you have a use for
the electricity than you could support a rather large house battery bank.

If I was able to build something that could have that size of PV array and particularly if no grid connection was available (which I assume is your case) , depending on any shading obstacles I would look at having the roof orientated so that say 50% of the panels faced south, 25% faced East and 25% faced West so that the number of hours that some power was available was greater than if all the panels faced South.

Obviously with an array of that size I would split the panels and wire them as though they where a number of smaller arrays each with their own mppt charge controller , to both keep the voltage/amperage down to sensible levels and build in redundancy.
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Re: Renewables to replace our diesel genny

Post by adam2 »

A renewable energy system on the scale proposed should meet almost all of your electricity demand. I would strongly advise keeping the generator for any exceptional demand.

Fork lift truck batteries are back in favour for off grid homes as the economics have altered in favour of this type.
The inverter should be duplicated. Lighting and refrigeration might be best at battery voltage.

For a large 24 volt system, automotive fuses are not suitable, at least not for use close to the battery.
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Re: Renewables to replace our diesel genny

Post by PS_RalphW »

The Nissan Leaf has had bi-directional charging from day one. Unfortunately this is on the Chademo DC charging port, and as yet there is no domestic bidirectional Chademo charging station available on the open market. One is undergoing trials, but it will be expensive.

https://wallbox.com/en_uk/quasar-dc-charger
https://www.voltaev.co.uk/products/wallbox-quasar

£5600 ex VAT

The best small electric car at reasonable second hand price has to be the Renault Zoe, but there are so many variants on the market (many with leased batteries) you need to do your homework. Also, they have relatively poor reliability by EV standards. For the distances you are talking about a 30KWh Leaf sounds the best compromise.

The only other EVs with bi-directional charging are brand new and over £40,000
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Re: Renewables to replace our diesel genny

Post by Potemkin Villager »

Do not even think about a small wind turbine unless you can locate it in the clear
well clear of all buildings and obstructions. Other wise a relatively short trouble free life
will be an even shorter trouble free life. I hope folk at CAT have told you this already.
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Re: Renewables to replace our diesel genny

Post by Catweazle »

Here's an off-the-wall idea to pick apart for fun. Why not a VAWT on top of the new building ? With the shaft feeding down into the building you could use it to pump water, drive machinery, or perhaps even to charge the car via the regenerative braking system if you could connect to it.
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BritDownUnder
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Re: Renewables to replace our diesel genny

Post by BritDownUnder »

Catweazle wrote: Fri Jul 23, 2021 10:18 pm Here's an off-the-wall idea to pick apart for fun. Why not a VAWT on top of the new building ? With the shaft feeding down into the building you could use it to pump water, drive machinery, or perhaps even to charge the car via the regenerative braking system if you could connect to it.
You could also try one of those "Australian" style water pumping wind mills as they provide a reciprocating movement via a vertical shaft down to the ground level. If you really want to go VAWT you can get some on the cheap online site with bay in the name. From memory there was a company in NZ about 20 years back that made VAWTs called solwind. Very little trace of them on the net now but their prices were eye watering - maybe 50,000 pounds equivalent for a 10-20kW turbine. They had about 6 blades on a VAWT arrangement on a lattice tower.

Or maybe let your engineering skills let you design your own.
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Re: Renewables to replace our diesel genny

Post by Potemkin Villager »

BritDownUnder wrote: Sun Jul 25, 2021 3:20 am
Catweazle wrote: Fri Jul 23, 2021 10:18 pm Here's an off-the-wall idea to pick apart for fun. Why not a VAWT on top of the new building ? With the shaft feeding down into the building you could use it to pump water, drive machinery, or perhaps even to charge the car via the regenerative braking system if you could connect to it.
You could also try one of those "Australian" style water pumping wind mills as they provide a reciprocating movement via a vertical shaft down to the ground level. If you really want to go VAWT you can get some on the cheap online site with bay in the name. From memory there was a company in NZ about 20 years back that made VAWTs called solwind. Very little trace of them on the net now but their prices were eye watering - maybe 50,000 pounds equivalent for a 10-20kW turbine. They had about 6 blades on a VAWT arrangement on a lattice tower.

Or maybe let your engineering skills let you design your own.
I can assure you the world does not need even more "novel" wind turbine designs!
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Re: Renewables to replace our diesel genny

Post by Catweazle »

VAWT are tried and tested, and although they are not reckoned to be as efficient as more popular designs they do have plus points. For example, they work near obstacles that cause wind to change direction frequently.

I became interested in VAWT when I cut a hole in a hedge between two fields, the wind whistles through the gateway even when it's almost still elsewhere, because the hedgerow funnels it. For me this could mean a couple of small VAWT without losing any field space. I bought a job lot of 2 and 3kw permanent magnet 3 phase servo motors a while back for this project, gradually I'm finding bearings and other components. The foils themselves will be made here based on a modified NACA design I found online. There is a lot of information on foil design available, but building the right mould is quite a job, so I aim to get it right first time and have a saleable product.

Ideally most of the hardware required would be already available cheaply, for example car wheel hubs and joints.

I like the idea of spring loaded foils that automatically "open out" to prevent overspeed, linked together to keep the whole thing balanced or possibly tripping a mechanical brake in emergency - could be another cheap car part here.

Any ideas welcomed.
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Re: Renewables to replace our diesel genny

Post by clv101 »

kenneal - lagger wrote: Fri Jul 23, 2021 1:51 pm I've been planning a new barn/shed for wintering our animals and that would give us a roof where I could put about 20kWp of PV on a ridged roof or 40kWp if it was monopitched from north to south. This, combined with a wind turbine or say 6 to 10kW, would enable us to run on renewables most of the time with the generators as a backup. I was also thinking about replacing our car with a small plug in electric car and possibly combining that with the energy storage. We have 1350Ahrs of batteries at the moment which are run to 50% Depth of Discharge and I was thinking of doubling or even trebling that. The car doesn't get that much usage, probably ten miles a day on average with some days at about 70 miles and the occasional 220 mile round trip to Wales or 140 mile round trip to the beach.

My daughter, son-in-law and family live with us and they have two cars, one of which is a small run which they use mostly and could be replaced with an small electric car when the time comes for its replacement. That car probably does twice the mileage of ours so it is still not a massive usage.

Any thoughts would be appreciated.
We're off-grid and have around 10 kWp of PV, in three arrays, all due south, some at a low elevation around 14 degrees others more like 34 degrees. The angles are optimal for the buildings not the solar.

While panels themselves are very cheap these days - the (good quality) associated charge controllers, inverters and batteries remain expensive. 20 kWp should be plenty. Worth considering adding just 2 or 3 panels vertical on the east and west gable end of the barn, doing so really helps the morning and late afternoon yields.

Battery wise, I'd give serious consideration to Li these days, they are approximately twice the price on day one the same usable capacity - but are much easier the live with, more temperature tolerate, no off-gassing, no need to top up water, don't suffer damage from a full discharge, and come with long (~10 yr) warranties.

Grid-tie inverters are a lot cheaper than quality off-grid inverters - I've seen a few people use a small, decent off-grid inverter to spoof the grid with the bulk of the load taken by a regular grid-tie mppt/inverter.

EV charging for the kind of miles you're talking about shouldn't be an issue - but things would be a lot easier if you just accept from day one to charge off-site for a couple months a year. Paying to charge in Dec and Jan will be a lot cheaper than dimensioning the off-grid system.

We have no wind and no generator and manage just fine.


How hard would it be to connect to the grid? The grid is dramatically lower carbon now than a decade ago and it saves a lot of money and complexity to connect to it where feasible. Here's something I wrote a few years ago about the merits of a grid connection from an off-grid point of view: http://www.oneplanetcouncil.org.uk/wp-c ... _01a-4.pdf
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Re: Renewables to replace our diesel genny

Post by Catweazle »

How does a PV system stack up as a "doomer" prep ? Even if not grid tied, is the life of the panels or batteries a concern ?
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Re: Renewables to replace our diesel genny

Post by adam2 »

An off grid system is a most useful doom prep.
The PV modules should last almost forever, though perhaps with a declining output.
Batteries have a more limited life in the longer term, though even a very much reduced battery capacity will power limited lighting after dark, with higher power uses being confined to daylight.
VERY basic lead acid batteries can be home made and should last for many years. The materials for manufacture keep forever.

Theft or looting of the PV modules could be a concern, but arguably less of a concern than in years gone by. Huge and undefended arrays in fields are an easier target than those on domestic or farm buildings, the occupants of which may be armed.
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Re: Renewables to replace our diesel genny

Post by kenneal - lagger »

We were quoted £18000 for a grid connection nearly 40 years ago now and at the time an electrical engineer friend said that £8000 of that would be the cost of the copper cable. God knows how much the copper would be now but it is about half a mile underground with half of that under the public highway !!
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Re: Renewables to replace our diesel genny

Post by Potemkin Villager »

Catweazle wrote: Sun Jul 25, 2021 11:09 am VAWT are tried and tested, and although they are not reckoned to be as efficient as more popular designs they do have plus points. For example, they work near obstacles that cause wind to change direction frequently.

I became interested in VAWT when I cut a hole in a hedge between two fields, the wind whistles through the gateway even when it's almost still elsewhere, because the hedgerow funnels it. For me this could mean a couple of small VAWT without losing any field space. I bought a job lot of 2 and 3kw permanent magnet 3 phase servo motors a while back for this project, gradually I'm finding bearings and other components. The foils themselves will be made here based on a modified NACA design I found online. There is a lot of information on foil design available, but building the right mould is quite a job, so I aim to get it right first time and have a saleable product.

Ideally most of the hardware required would be already available cheaply, for example car wheel hubs and joints.

I like the idea of spring loaded foils that automatically "open out" to prevent overspeed, linked together to keep the whole thing balanced or possibly tripping a mechanical brake in emergency - could be another cheap car part here.

Any ideas welcomed.
I really don't want to be negative about your enthusiasm for this project.

These were all thoughts that went through my mind 35 years ago when I got involved in a small VAWT project. All I can say is that my (the electrical bits) worked but nothing else did for very long. Maybe I should write a detailed account of what went wrong but I do not want to bore you. The main trouble were the un restrained egos of two other people in the project when I later realised that they really did not understand the mechanical forces they were dealing with.

I vividly remember the night of my last day on the project. During a storm when the inadequate rotor brake (a Mini rear wheel hub assy) was not up to the job the turbine got away into overspeed. I don't know if you have ever been near an over speeding wtg but if you are used to being in control it is a salutary if terrifying experience. The next stage was the inadequacy of the blade attachment became obvious as one of the 1.5 M blades flew past over head and the now unbalanced turbine started shaking itself apart.....

At this point we ran and were lucky not to be seriously injured or killed. We were not even wearing hard hats!

The next day the shed blade was found 3 Km away.

Good luck and take care.
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Re: Renewables to replace our diesel genny

Post by adam2 »

If you fear that a wind turbine is going to suffer "non passive failure" then I suggest RLF, which may be politely translated as "run away very quickly".

I have only seen a non passive failure twice, both were home made. One caught fire and the other shed the blades.
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