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Understanding Solar Energy

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261 points chmaynard | 3 comments | 20 Mar 25 12:09 UTC | HN request time: 0.691s | source
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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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kavalg ◴[21 Mar 25 08:59 UTC] No.43433336[source]▶
Why are people even considering an electric heating element, when you can get at least 2-3 times the efficiency of a DHW heat pump that would probably cost you ~ $4000. In my experience, I have found that for PV panels it is often the roof area / orientation that limits the energy capacity that you can install. Installing a heat pump instead of resistive heater can effectively reduce this 2-3 times.

Yes, heating DHW with a heat pump is not that trivial. There could be problems when the tap water is hard (limescale problems in heat exchangers), you often need 2-3 times larger tank in order to cover the daily cycle, but still looks more efficient than a big battery and an electric heater.

PS: I've accumulated lots of knowledge on the topic. DM me if you are interested in exchanging on this.

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jajko ◴[21 Mar 25 12:35 UTC] No.43434893[source]▶
Heat pumps come with a lot of restrictions. What about constant noise? Plus stating that they are cheap ain't correct. Our housing unit in Switzerland recently needed to replace older oil heater and one of the options was heat pump... which was by far the worst choice based on various criteria and we at the end voted for the oil again.
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kragen ◴[21 Mar 25 12:38 UTC] No.43434916[source]▶
How much was the cost, for how much heating capacity?
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1. jajko ◴[21 Mar 25 16:41 UTC] No.43437854[source]▶
Sorry don't remember exactly, it was for 17 rather large apartments/semi houses (120-190m2), IIRC to the tune of 200k. Heat pumps would also require additional space to be put in, something we didn't have easily (not without some remodeling of whole area). They would be in the face of everybody's windows, another drawback combined with noise that was unavoidable as per proposition from vendor.

Another issue was that they were not available for a long time (around 6 months delivery time with no guarantee), something not relevant here but it also affected decision of owners.

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2. kragen ◴[21 Mar 25 16:41 UTC] No.43437860[source]▶
I appreciate the information!
3. kavalg ◴[22 Mar 25 07:54 UTC] No.43444259[source]▶
Thanks for the info! Now it is much easier to understand your concerns. It is a rather big installation that you have here, in the range around 100kW (if both space heating and DHW are considered). Such systems (aka chillers) are usually installed away from buildings or on the rooftop if local regulations allow it.