Going off grid

[Colin G3YHV]

I wonder if any members have thought about going off grid with electricity ?
What with the nutty price of power these days. Plenty of scope for playing with pic chips
on this project. I connected my 55inch oled tv and big audio amp to   a 12v car battery the other day
used a cheapo inverter from ebay, the battery had not been charged since Xmas and ran it for three hours.
I have plenty of room for south facing panels here. Any thoughts ?
Colin G3YHV

[John Drew]

I live in Australia and even here the numbers don't stack up with one exception. It's for those who have built a home some distance from the grid and have to pay many thousands for a connection.
The above is based on a commercial installation of everything. So as a home exercise and a willingness to be frugal with power use it might just pay. The life of Li-ion batteries is still debatable on a cost benefit basis.
Those who have been successful have achieved it with specially designed homes and a strong commitment to improve the environment by using less energy.
A big save is to change your HWS to a solar one. They work well in Oz as you would expect.

Silicon Chip Magazine had an excellent article a few months back.
John
VK5DJ

[chris_cb_uk]

@Colin G3YHV I too am looking at harvesting solar. Looking more at the storing element too.
I see the main issue currently is the terrible feed in tariff its not worth putting back into the grid. But storing the energy to use when needed makes more sense.

I've looked at two solutions, a hybrid inverter with batteries to store and recharge in the day, to use later in evening to lighten the electric meter. Alternatively sinking the surplus energy into an immersion heater to heat the hot water, reducing the gas requirement for hot water.
It seems many of the inverters have rs485 for communication so wouldn't be hard to interface a pic so you can control the use / routing of the generated power to make best use.

We have a flat roof extension and looking at our local council for the area we are in as long as the elevation off the roof is 20cm or less it falls under permitted development not needing planning permission. However it seems the energy company wants to know if you hook up a grid tied system as they fear you putting too much back into the system and the network not being able to cope. There appears to be some considerable fees involved if you exceed 4kw generation, which doesn't really make sense considering our mains fuse is rated at 100A. Seems a little bit of a hidden tax to make money knowing you'll be spending less with the supplier in the long run...

[top204]

I was looking into getting a wind turbine to run my office at home. The 1.5 metre types work quite well and give enough for storage. They were approx £1000 at the time, so after a couple of years, it would have paid for itself.

Back then, we lived in North West Norfolk in the UK, so the wind was, generally, quite good because it is so flat, and we had a detached house. I was going to buy, cheap, old car batteries for storage, and this would have ran the computer and maybe a small heater in the office, thus saving the electricity on a room that was always full of me, 24/7 sometimes. :-)

But then, my injury happened, and I made the big mistake of moving house. So that went out of the window. :-(

[shantanu@india]

India's economy is primarily agro-based and it is no wonder that solar powered irrigation pumps are gaining importance day by day. These are basically variable frequency drives where the DC bus is the voltage delivered from the solar panels. No storage batteries since most of these pumps work during daytime. Moreover maintenance of batteries is an additional burden.
In the homefront people living in big cooperatives are installing so called 'import export' meters which supply the solar generated excess power back to the grid. These take the help of inverters with 'active front ends' which can synchronize with the grid.

[chris_cb_uk]

@shantanu@india the problem with the export meters and selling back to the grid is the supplier pays about 1/4 the cost that a unit costs to use. That is why I was looking at a storage means to improve efficency of unit usage, be it by heating the water tank for hot water or heating, or batteries for later higher power usage. My long term plan is to install revers heat pump air conditioning to provide heat as well as cooling powered by electric.

According to the smart meter we have the typical house idling is about 300w, so even a panel and inverter able to generate 400w would reduce the idle house to zero.

[trastikata]

The problem here (and elsewhere I'd guess) is how log it will take for the initial investment and the running costs to pay out. My latest calculations, in my case and region, show that it would take me about 20 years to pay for the "privilege" of having a "green" home.

Thanks, but no thanks, I don't want pay a second mortgage just so that some large multinationals can sell solar panels and inverters at 500% profit for merchandise, manufactured in China.

[chris_cb_uk]

I don't really see the markup being that much on panels and inverters. A reasonable 3kw inverter is around GBP 450-900 and a 450w panel GBP 150-300. For small scale I don't think that's too unreasonable.
I see it more of a longer term investment of gradual chipping away at the bills rather than an immediate saving.
The panels are made much better than 20 years ago, higher power with lower reductions in efficency over time. Its just a shame that the overall efficency of a panel is less than 21%!

[trastikata]

Chris,

I'd guess it really depends on the region. I've calculated I'd need about 9-10kWh installation in my house, which in Canada costs about 25 000 dollars. About 2.60-3.00 dollars per Wh.

My average hydro bill (heating is electrical) for the past year has been 110 dollars/month. Leaving inflation, interest rates etc aside, if I were to make the investment now and assuming no wear and tear on equipment and completely going off the grid, it would take me 25 000 / (12 * 110) = 19 years to pay it out.

However, if there were to be minor maintenance costs, then the 19 years become say 21 years. At average lifespan of 25 years for the PV panels it doesn't really pay out here.

Now, there's one very important moment here - I still want to keep my connection to the power grid in case of extreme weather conditions or PV failure, so I still will have to pay the monthly maintenance cost in the hydro bill.  The 21 years payout period is no longer 21 but more than 25 years ....

My point is make sure it is really worth converting to PV energy where you live.

[charliecoutas]

The UK government seems to think that the only possible way of heating our homes, once gas boilers are not allowed, is by using heat pumps. Do any of you have any experience of these? A pal of mine at Bletchley said he got rid of the heat pump in a house he bought because of running costs.

Sorry if this is going a bit off-topic.

Charlie

[RGV250]

Hi,
Slightly different but I had a heat pump tumble drier, it took an absolute lifetime to dry clothes and they never really felt dry. The problem is the supposed "intelligent" people only look at the power rating and think it is wonderful. They do not seem to have the intelligence to work out if you have to run it 3x as long does it is not as efficient.

Totally off topic thing but the same is happening with the E10 fuel, it might be greener on paper but you use a lot more that the 1% difference they say.

Bob

[chris_cb_uk]

I see the problem with heat pumps is that they're being missold. They're being sold as a replacement for a gas boiler. That's not the case as they get nowhere near temperature to offer the same radiator and hot water temperatures. Even the latest ones only heat water to about 60deg c. If however they are installed as part of a wet underfloor heating, that's a different story. 10 years ago when I was an electrician a customer had this installed and it worked great. But for underfloor your only looking at 23-25 degrees.
There isn't just a slot in replacement without infrastructure change.


My heat pump air con at my workshop does heating and cooling. It's very efficient and heats the space to about 18c in winter when it's - 2c outside. They do loose efficency though with external temp.

[Colin G3YHV]

Some interesting comments  -  thanks
These charge controllers look good value
https://uk.renogy.com/products/charge-controllers
I am suffering from Covid at the moment and only feeling about 10%
Contracted it at the local  radio club last Friday  -  now about five other members also have it!
Happy days  -  Colin

[LeonJ]

I've been 100% off-grid now for more than 2 years.

Since I live in the country outside Pretoria, South Africa, I had to purchase power directly from the main Supplier where connection fees are high.

I have 3 X 5kW hybrid inverters in parallel with 7 X 4.8kWh Li-Fe-Po4 batteries and 24 X PV's at 375W each (8kW peak). This serves all my needs with energy to spare.

In my case the ROI is less than 4 years but that's largely due to the high connection fees I had to pay.

Of course we also have cloudy spells and for this I have a back-up generator that is needed on average for about 6 to 8 hours monthly.

The most effective way to reduce energy consumption is to install direct heating solar collectors for hot water. This does not always reach desired
water temps but it does reduce electricity consumption by quite a lot. (in my case by about 40%). The type I have is the Evacuated Tubes.
(I had heat pumps before but they were definitely not worth the cost, noise, servicing etc.)

I have learned that "prioritized load management" goes a long way to improving total system efficiency and yield.
When I have excess electricity (often), I charge the geyser temps higher (it's a thermal battery) and fill water tanks and compressors.
A bit of scheduling also helps a lot i.e. run dishwasher and washing machines in daytime when there is good sun.

A note on storage batteries:
The older (cheaper) lead-acid, AGM gel or "flooded" type batteries have a typical charge/discharge cycle life of 400 to 600 cycles and then is only about 75% energy efficient (100 W in, 75W out)
The current Li-Fe-PO4 chemistries have 4000 to 6000 cycles and have better than 95% energy efficiency.
In my view it's a waste of money to buy the older type chemistries. They need replacing typically every 3 to 6 years.

So far, this has been an absolute blessing. No load-shedding, interruptions, price hikes, spikes, drop-outs etc. INDEPENDANCE!

 






 

[charliecoutas]

"No load-shedding, interruptions, price hikes, spikes, drop-outs etc. INDEPENDANCE!"

LeonJ, that's very encouraging. Thanks for your feedback. Well done!

Charlie

[keytapper]

Just a bit of curiosity, what is the estimation of the cost per KW for such installation?

[RayEllam]

Hi all,
My first post in a while......iv been living in the Philippines for the past 16 years and installed my first DIY hybrid system around 7 years back. Iv learnt a lot since then on not what to throw your cash away on. Here are my basic guidelines based on systems I know design an install here in the PH.
1. Buy branded grade A panels, they cost around 15% more than generic junk.

2. Buy an inverter from a company that has been around for more than 10 years, all of the stuff I install is china made BUT well designed AND with quality components in side. At the moment I'm using DEYE hybrid inverters, they are half the cost off euro/Aussie stuff and are sweet. So even if a high price inverter will do 10 years and the DEYE will do 7 then your still on top cash wise.

3. For hybrid systems use LIFPO4 battery's, 5000 cycles equates to 14 years of use and they are now at around the same cost as high grade LA batteries and totally outperform the latter.

4. The ROI for my customers here in the PH on my installs are 4 years for a grid tied system and 7 years for a hybrid system. Hybrids are more popular here due to the many brownouts we experience.

[RayEllam]

I was looking into getting a wind turbine to run my office at home. The 1.5 metre types work quite well and give enough for storage. They were approx £1000 at the time, so after a couple of years, it would have paid for itself.

Back then, we lived in North West Norfolk in the UK, so the wind was, generally, quite good because it is so flat, and we had a detached house. I was going to buy, cheap, old car batteries for storage, and this would have ran the computer and maybe a small heater in the office, thus saving the electricity on a room that was always full of me, 24/7 sometimes. :-)

But then, my injury happened, and I made the big mistake of moving house. So that went out of the window. :-(

Do not use cranking battery's, they will be dead after 6 months, they are designed for short bursts of high ampage current and a constant charge current.
.....been there, done that, tee shirts available 🤔

[LeonJ]

Hi all,
My first post in a while......iv been living in the Philippines for the past 16 years and installed my first DIY hybrid system around 7 years back. Iv learnt a lot since then on not what to throw your cash away on. Here are my basic guidelines based on systems I know design an install here in the PH.
1. Buy branded grade A panels, they cost around 15% more than generic junk.

2. Buy an inverter from a company that has been around for more than 10 years, all of the stuff I install is china made BUT well designed AND with quality components in side. At the moment I'm using DEYE hybrid inverters, they are half the cost off euro/Aussie stuff and are sweet. So even if a high price inverter will do 10 years and the DEYE will do 7 then your still on top cash wise.

3. For hybrid systems use LIFPO4 battery's, 5000 cycles equates to 14 years of use and they are now at around the same cost as high grade LA batteries and totally outperform the latter.

4. The ROI for my customers here in the PH on my installs are 4 years for a grid tied system and 7 years for a hybrid system. Hybrids are more popular here due to the many brownouts we experience.

Agreed on all points! Also, if you don't discharge the LIFEPO4 down to 20% but say 50%, the estimated cycle life will improve. Some specs claim up to 10000 cycles (27 years) if you only discharge down to 50% per daily cycle. This, of course, remains to be seen.

I also agree on cranking batteries. They are a bad choice for cyclic charge/discharge usage.

My system cost (approx in US Dollars):
3 X 5kw inverters:          USD 1800
7 X 4.8kwh LIFEPO4:     USD 9300
24 X 375w panels:         USD 3200
Switch-gear + sundries: USD 333
                  Total:            USD 14633

Estimated ROI: 3 to 4 years (but electricity prices are rising sharply, so this will be sooner)
Estimated System Life: 20 years
Independence: Priceless!
Satisfaction: 100%

I've noticed the price of panels and LIFEPO4 batteries have decreased a bit over the last 2 years by about 10%.
Inverter prices seem stable or perhaps increasing slightly.