diy solar

diy solar

How efficient is your generator?

OffGridInTheCity said:
I've gradually come to learn that fossil fuel generator power is not 'the best'. The mechanical/physical *effort/horsepower* required to generate electricity by engine or water or wind is huge. PV is just sooo much smoother, quieter, no mechanical maintenance etc etc. The horsepower/noise/fuel for 6000w of charging power just seem like a loosing effort compared to panels.

My biggest disappointment is heating the house. I've tracked my whole house, highly efficient, 4-ton heat-pump over a few years now with some years being 100% electric and some being natural gas assist. I live in a mild Zone 4 climate and thought, 100% electric + PV + generator (in winter) = no problem.

But I've come to see generators as not practical or best use of fuel for heat - even with a heat pump + mild climate (avg 35F low).

For example, to do 100% electric heat for the 4 months of winter in a 2600sq ft house I need ~5600kwh of power. My 14.5kw PV (51 panels) get's me ~2400kwh of that leaving a 3200kwh gap. Using 200 Therms of natural gas (~200gal of propane) the heat-pump 4 month power use drops to ~2400kwh.

3200kwh / 200gal means I'd need to generate 16kwh / gal of propane to go 100% electric route with the same efficiency as burning the fuel for heat. Turning it around, I'd need 533gal of propane instead of 200gal for the same heat + maint to mechanically generate 3200kwh It's just more efficient to use fuel for heat than to generate electricity for heat.

Deeply disappointing compared to my original rose colored glasses.

However, if I could just build a container with 40 or 60 or 80 used EV batteries and store 4000kwh of power during summer to be used during winter - it would only be 1 cycle per year so used EV batteries should work great!
Click to expand...
Double your panels and should nearly cover winter usage.
 
Just wrapped up a 50minute propane test on the duel-fuel Champion 8000w Model 100297 with Chargeverter set to 100a -
https://www.championpowerequipment.com/product/100297-8000w-electric-start-dual-fuel-generator/
1712261480993.png

Generator -> Chargeverter performed smoothly (no issue with generator) as expected.

Fuel: 30lb propane tank went from 41lbs -> 34lbs = 7lb drop which is ~1.6gal using 4.3lbs/gal because it's 50F today.

Generated 5.24kwh on 1.6gal = 3.2kwh/gal of propane which is way lower than expected. **Used cheap bathroom scale to weigh tank**
1712347230072.png
Will do another run in a few days (give neighbors a break) and re-weigh the tank and do a follow up post on propane consumed.

Here's a bunch of detail in the form of a 'snapshot' of my dashboard figures at one point during the run....
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With propane I just assume 50.3 MJ/kg = 13.97 kWh per kg or 6.34 kWh per lb.
7 lbs = 44.4 kWh

5.24 out / 43.8 in = 11.8%

OffGridInTheCity said:
**Used cheap bathroom scale to weigh tank**
Click to expand...
Both precision and accuracy of such scales is typically poor and especially at lower weights.

I once had two gym weight plates (~20kg and ~15 kg) weighed to the nearest 5g at two verified transit centre weight scales. I used to use them for calibrating strain gauges in bicycle power meters but also once used them to calibrate a bathroom scale. If you are friendly with a local service provided with a verified scale you could do a before and after with their scale.
 
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