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Understanding Solar Energy

(www.construction-physics.com)
261 points chmaynard | 9 comments | 20 Mar 25 12:09 UTC | HN request time: 0.413s | source | bottom
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bryanlarsen ◴[20 Mar 25 14:23 UTC] No.43423941[source]▶
Great article. Unfortunately his California duck curve graph only shows 2023. A graph including 2024 shows how batteries are dramatically flattening the duck curve:

https://cdn-ilcjnih.nitrocdn.com/BVTDJPZTUnfCKRkDQJDEvQcUwtA...

https://reneweconomy.com.au/battery-storage-is-dramatically-...

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Calwestjobs ◴[20 Mar 25 17:00 UTC] No.43425755[source]▶
Hot water tank heated by electricity and powering on at noon is flattening curve. You can say hot water tanks are cheapest, simplest and fastest deployed energy storage device.

Solar + hot water tank can provide any house in US with 100% solar hot water (from PV!) for 80% of time, remaining 20 % of time you can have 10-99% solar heated water.

So we should focus on saying to people that if they buy solar and add electric heating element to hot water tank, then PV system will pay itself much sooner and their batteries will last longer. Becasue it is known and predictable load, you need hot water every day. And hot water is order of magnitude more energy then TV, lighting...

By lowering household usage like this we can make energy transition faster, cheaper.

Also proper construction - house heated only 10 days in a year - https://www.youtube.com/watch?v=5KHScgjTJtE

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dzhiurgis ◴[20 Mar 25 19:48 UTC] No.43428024[source]▶
My hot water heats up in less than 2 hours and if I don’t fire it up at night I won’t have hot water in morning.

At this point getting some batteries would likely be cheaper than new boiler + plumber to install it.

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1. PaulDavisThe1st ◴[20 Mar 25 22:00 UTC] No.43429470[source]▶
It loses heat overnight, or you use all the hot water contents overnight?
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2. dzhiurgis ◴[21 Mar 25 01:52 UTC] No.43431104[source]▶
Sun stops producing useful amount after 6pm which coincides with dinner and whole family taking a shower.
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3. NullPrefix ◴[21 Mar 25 07:33 UTC] No.43432747[source]▶
Increasing water heater capacity might be cheaper than increasing battery capacity.
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4. dzhiurgis ◴[21 Mar 25 09:54 UTC] No.43433712{3}[source]▶
New cylinder - 1.5k NZD + half day of labour (so another $500). My current one stores about 6-8 kWh.

15kWh battery - 5.5k NZD + and hour of DIY.

So technically battery is more expensive but more useful.

Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).

Another thing with battery I can charge with whatever solar excess I have, but with hot water my only option is 16A.

Either way I do not care ATM - I export using spot price which has been 2x of what I actually pay for power - https://www.emi.ea.govt.nz/Wholesale/Reports/W_P_C?DateFrom=...

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5. kragen ◴[21 Mar 25 10:52 UTC] No.43434108{4}[source]▶
Higher temperature hot water requires more expensive plumbing, too.
6. nimos ◴[21 Mar 25 11:18 UTC] No.43434302{4}[source]▶
FWIW you can get thermostatic mixing valves that limits the maximum temperature of the water by mixing in cold water. Lets you run the tank hotter but have the same outlet temp. Fairly cheap I believe.
7. NullPrefix ◴[21 Mar 25 11:32 UTC] No.43434398{4}[source]▶
>Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).

Your water heater temperature isn't exactly my business but please look into sanitary norms on minimum safe temperature. Water heaters have standing water and bacteria might start living there if the temperature isn't sufficient. I think legionnaires' disease is one of the most prevalent dangers.

8. hnaccount_rng ◴[21 Mar 25 12:16 UTC] No.43434723{4}[source]▶
Can you legally put a 15kWh battery on your system without anyone signing off on it?
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9. dzhiurgis ◴[21 Mar 25 19:26 UTC] No.43439952{5}[source]▶
48 volts bby