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Understanding Solar Energy

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261 points chmaynard | 4 comments | 20 Mar 25 12:09 UTC | HN request time: 0.415s | 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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epistasis ◴[20 Mar 25 17:26 UTC] No.43426144[source]▶
Converting a gas water heater to electric and/or solar is one of the best bang for the buck on decarbonization too. Something that should be done before buying an electric car or swapping out your gas furnace for a heat pump. Though I'm terrible at following my own advice, I still have a gas water heater, just because I needed to replace my car and furnace before I needed to replace my water heater. That said, the sunk cost fallacy applies to carbon emissions just as hard as it does to dollars so I have little excuse for not replacing it except laziness (and space on the breaker panel...)
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fho ◴[21 Mar 25 07:37 UTC] No.43432773[source]▶
Problem being that electric water heating is a lot more expensive in e.g. Germany where gas prices are lower than electricity prices per kWh delivered. (~12 vs. 39 eurocent per kWh)

So blindly converting a gas water heater to electric will roughly quadruple your water heating cost.

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ben_w ◴[21 Mar 25 09:01 UTC] No.43433341[source]▶
Only a problem when you're limiting yourself to resistive heating. Heat pumps can heat water, not just air, and are several times more efficient than resistive.

I've got a heat pump, and I'm in Germany.

Also, if you're in Germany, you can get a balcony PV system from half the supermarkets a few hundred euros, and those are designed to be installed DIY without needing an electrician. Limited power, sure, but way cheaper than €0.39/kWh delivered:

• https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800...

• https://www.kaufland.de/product/502015379/?search_value=balk...

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1. fho ◴[21 Mar 25 13:18 UTC] No.43435319[source]▶
We actually do have a Balkonkraftwerk im Garten :-)

Now that the sun is out for longer periods each day we are "wasting" energy to the grid a lot. I don't really see how to capture that energy though.

1. Buying a battery quickly shifts the break even points to decades. Without a battery I estimate 3-4 years. 2. I would love to heat water, but renting a place limits my options a lot. I was looking at electrical boilers to supplement the gas heater. But we are limited on space for small heaters below the sink and big heaters in the main water path. (Also we can't change the plumbing for legal reasons.) 3. The next best thing is some imaginary insulated water heating kettle that I can control to only use exactly the excess energy. No idea if such a thing exists.

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2. notTooFarGone ◴[21 Mar 25 15:40 UTC] No.43436969[source]▶
You should calculate the battery parts again. I'm currently installing mine in Germany and the cost parity is getting close.
3. Huppie ◴[22 Mar 25 08:44 UTC] No.43444400[source]▶
You probably thought of this already but we mostly do load shifting. If you have moderate PV output (like with balcony solar) that can probably use up most of your production.

Consider running the dishwasher (if you have one) or washing machine / dryer (if you don't dry that in the sun directly) during the day.

Granted, we work from home _a lot_ and also have an EV so it's a lot easier to do load shifting for us, but just shifting the dishwasher and washing machine to 'sunlight hours' already made a pretty decent difference.

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4. fho ◴[22 Mar 25 13:11 UTC] No.43445475[source]▶
Yeah, we do that. Given that most home appliances use more than 800W (even in Eco modes) we often use more than our production.

E.g. our washing machine uses 1000W over a prolonged period of time which would be perfect to run on a sunny day. But it does so by switching the 2000W heating element so it averages to 1000W ...

So we repeatedly export 800W (without any form of reimbursement) and import the missing 1200W back.

And that is the case for all of our appliances. (I have a sensor to monitor that)

Don't know if more modern machines are better in this regard, our machines are about 5 years old now.

edit: I don't want to sound bitter about it. The Balkonkraftwerk works perfectly fine to power our base energy load.