Off Grid Options

[stevehaigh]

i'm thinking about going off-grid since the local electric company want to charge me mega-baht for transformer plus hookup

my idea is a combination solar, wind and backup generator

PV systems are costing about $1.80/watt in china these days so for say 3kw, that's about $6000.

a 3kw wind generator with tower, controller, inverter, etc is $2500

a 5.5kw LPG powered generator is 37000 baht here http://www.lpggen.com/

batteries, i don't know, lets assume another $2000 for now.

so VERY approx total is about $12000 or 360000 baht which is far less than what the fai faa guys want and the only ongoing bill to pay is LPG for the backup gen. by the way, the LPG generator burns about 0.36kg/kwh so that works out about 9 baht/unit

this is all very preliminary math but at least its in the ball park of what i can afford. my power use isn't high, i don't need A/C so all we run is fridge, fans, lights, tv and computers and a pool pump which can be set to run only when enough power available

any thoughts?

[Pacificperson]

When you are doing your calculations, remember that you burn kWh not kW. Your photo cells will generate for maybe 6 hrs/day and not at full power if it is not full sun. Anyway your 3kW of cells may give you 18kWh per day at best. Divide this by 24 hrs and you get 750 watts average consumption. The two other things that you need to factor into your planning are the need to maintain and replace the batteries. The contacts have to be cleaned routinely and the cells may last 8-10 years if you buy good ones and do not abuse them. The genset will need an oil change every 50 to 100 hours of running time. One way to lighten the load on the system is to use an LP gas fridge, but your wife may hate it. You can do your laundry when you are running the genset to top off your batteries.

[InterestedObserver]

When you are doing your calculations, remember that you burn kWh not kW. Your photo cells will generate for maybe 6 hrs/day and not at full power if it is not full sun. Anyway your 3kW of cells may give you 18kWh per day at best. Divide this by 24 hrs and you get 750 watts average consumption.

Your overall system will not operate at 100% efficiency. The actual kWh available will be significantly less than calculated above.

[seedy]

I ran PV cells to power my motorhome in mining camp during the summer.

The best ever efficiency was 60 %, with 40 % being the average output from a theoretical max output.

After a few years, I found that a combination of PV and a genset was the best. Use the generator to top up batteries and for large loads, and the PV to keep batteries topped up.

I was gone from aprox 0530 until 1830 every day, so no loads during the peak sunlight periods.

[Khun Jean]

I am planning the same, PV & Wind & Generator. However i will skip the battery bank, they are expensive and have to be replaced within a few years. I will have grid power available but it is more of a 'sport' to see how much i can generate myself.

When PV & wind have power available that is the time to use it. When it gets dark and no more wind, go sleep.

Instead of storing energy in a battery i am curious if you can store excess energy in compressed air tanks. It would just have to be enough to power necessities at night like some lights and maybe a fan or 2. A full freezer and fridge will have no problem staying cold enough during the night.

[InterestedObserver]

I am planning the same, PV & Wind & Generator. However i will skip the battery bank, they are expensive and have to be replaced within a few years. I will have grid power available but it is more of a 'sport' to see how much i can generate myself.

When PV & wind have power available that is the time to use it. When it gets dark and no more wind, go sleep.

Instead of storing energy in a battery i am curious if you can store excess energy in compressed air tanks. It would just have to be enough to power necessities at night like some lights and maybe a fan or 2. A full freezer and fridge will have no problem staying cold enough during the night.

You will have trouble stabilizing the power without batteries or an active grid connection.

[Khun Jean]

No i would have not! DC is a lot simpler and for AC there is enough electronics available (and if not then build it) to smooth things out. When the wattage or voltage is not within range for some appliances it will not cause appliances to function wrong, they will just be switched off.

If you absolute need it a simple ups on a few items will buffer it. So it will not be completely without batteries, sensitive equipment will be protected by ups. There will be however no battery bank to store the excess energy. Compressed air is a more 'low tech' and of course 'lower efficiency' way to do that. But as long as energy is conserved and you not use too much it will be sufficient.

[stevehaigh]

check out this quote (attached) for a 5kw off-grid wind/solar system with controller, inverter and batteries

that's less than 400k baht, very reasonable i think

5KW Wind-Solar Power Systems Quotation - 2011.05.12.pdf

[silentnine]

i've been cosidering these sort of optionsfor a farm ., we use around 5000bt per month on electric .. all on water pumps .. with a peak usage of 2kw for around 2 hours per day ..