I'm in Germany and keep seeing these, I always wonder what a 400w poorly oriented panel getting like 3 hours of sun a day is good for. If they weren't basically free thanks to tax reduction and other tricks I assume no one would get them
> installing a couple of 300-watt panels will give savings of up to 30% on a typical household’s electricity bill, but there are lots of variables that come with that claim. It depends on which direction the balcony faces and whether the panels are shaded part of the day.
My german electricity bill is around 1200 euros a year. Sign me up for a one-time purchase of 426€ to save ~360€ every year if I had optimal conditions -- call it 50% effective and it's still earned back in under 3 years. The thing lasts, what, a decade? More?
Yeah so depends on your cost per kWh, and usage time versus production time. My 800W of balcony panels can theoretically produce 3-4 kWh per day (they peak at about 550w of actual production), but they generally produce a lot less than that. This is because my usage during production time is both less than that and also very spiky (my power usage is often 0w or 100-200w base load, with 2kw spikes as the compressor in the refrigerator kicks on, or some other device kicks on). So the savings for me isn't 3 years payoff, it's probably more like 6. But yes, these panels will product for 25-30 years. So yeah, they can pay for themselves very quickly depending on your usage patterns.
I'm in the US, and over here we also have some other complicating factors (here we have 2 sets of breakers that are 180 degrees out of phase and so the solar panels can only feed into one half of the breakers without extra complications. I only sort of understand this, someone else can explain better), so solar panels plugged into the balcony that don't backfeed straight to the grid can only cover a subset of the usage. In Germany you have 240v power so I would assume you would hit payoff very quickly.
Have to also consider the opportunity cost of that upfront cash. Those numbers sound worth anyway, but the 5 year break-even mentioned in the article is more questionable, and that's with subsidies.
(I'm too late and can't edit anymore, but I just noticed upon re-rereading that it says "couple of 300W panels" in the quote and not just "a 300W panel". My math (though done with a 450W panel for an example sales price) is likely off in the wrong direction. Sorry about that.)
"Poorly oriented panel" can equally well be described as "generates most of its power in the evening, when you have gotten home from work and want to use electricity".
It's better to get power at a useful time, even if that means the panel only generates half as much as it could, because storage costs far more than panels.
A 400W half decently oriented panel (i.e. south facing balcony, 60 degree angle) is sufficient to run your AC to cool your 50sqrm apartment during summer for free.
In the summer the optimal angle where I live (35.5º S) is 12º. Panels lying flat on the lawn are losing only 2% from that. Just now, near the equinox, panels lying flat on the lawn lose around 18% at noon.
I'll find a way to prop them up at 50º for winter when the time comes for that (April or May), though that's for sunny conditions. In our typical overcast in winter flat on the ground is probably still fine to catch the most diffuse light. I'll experiment when the time comes.
Right. I mentioned the suboptimal 60 degrees because many people hang it from the balcony (90 degrees) and the tilt it a bit, but usually not too much. From what I've seen 60 degrees seems like a good average number.
Yeah, in northern Germany vertical and 60º are pretty much equally good/bad in winter (75º would be ideal), but 60º will be getting 70% more power in summer than vertical, and is near ideal in spring/autumn.
Solar is cheap, non-peak-efficiency installs get to be the priority once you get the first 40% or so of production in solar.
This kind of thing just knocks the edges off of production and transmission costs. You get to the point where you're not trying to squeeze peak efficiency any more and you're just trying to fill in spaces wherever works reasonably well.
That's mostly true, but you're mistaken about the reason they're basically free: it's because the costs of manufacturing them have been dropping dramatically for 20 years, thanks to (in large part Chinese) manufacturing innovations, not because of things like tax reduction.
Maybe these can pull 700 watts on a sunny day? And you’d need a battery to store it. Would likely make 50 cents a day or less in electricity, on perfect days. The cost for a battery, panels, and install would be ~1000 euro (or more if it’s a bureaucratic mess).
I just did some modelling with the help of claude (which can write 200LOC+ numpy code faster than I can)
300 Euros crappy setup, 600 euros mid-range setup, 1200 with storage. (Extra) regulations is zilch, it's legal to plug and play these things up to 800W nameplate capacity.
I went with numbers for mid-range, vertical south orientation and offsetting 200W (without battery, any overproduction is wasted). This nets you an avarage of €0.32 per day - With practically nothing in winter, and maybe up to €1 per day on a PARTICULARLY nice summer day.
But altogether, that still adds up to something like Eur 116 per year, so your midrange system earns itself back in 5-6 years.
Not great, not terrible. Nothing to write home about, but free money is free money.
I built one in Utah which is the only part of the US where it's currently legal, so I can give you the numbers.
- 4x Hyundai 435W Solar Panels @ 167$ each for $670 total
- 1x EcoFlow Stream Microinverter for $257.
- Various cables, MC4 crimping kit, etc.. about $150
Grand total was $1077, I set them in direct sun on my patio and have generated 6-8kWh per day. At Utah energy prices (0.12 where I live), they will pay off in about 4 years. Somewhere like California with 4x the energy prices as here, it would probably pay for itself in <1 year.
My 1kW southern facing setup produces a little less than three kWh a day, about 1000kWh a year. A have a battery too so I manage to use most of that energy myself.
I use a battery -- 6kWh, 3600W inverter, with 6x 440W panels -- and don't feed power into the house wiring, but simply power the appliances in the same room as the equipment: Starlink, Mac Mini with 32" monitor, 16" i9-13900HX laptop, half a dozen small SBCs (5-15W each), fridge, espresso machine, air fryer, microwave, toaster, kettle, 4kW (output, 900W electricity) portable air conditioner, dehumidifier (250W). some LED lighting.
At the moment (spring) in half-decent weather all the above stuff is 100% off-grid. I'm still using grid power for hot water heating, dish washer, clothes washer -- all of which I do for free in my daily "Free Hour of Power" -- and for intermittent incidentals such as the water pump (e.g. runs for 15 seconds when I flush the toilet) and lighting in usually non-occupied rooms such as toilet, bathroom, and bedroom -- which together means I'm paying around 10c-20c per day over and above the fixed daily charge.
Rephrasing that to be more understandable because I didn't get this as it was: "Making sure no one buys expensive electricity from coal or gas plants when the grid is full of cheap renewable energy and almost-free stored energy."
I'm frankly still not sure what you're trying to say even if I understand the sentence now, e.g.: what free storage?! Isn't germany's projected storage capacity by 2050 somewhere between negligible and tiny?
That's like saying the cost of taking an additional bite from your food is very low once you have already bought it, if I'm understanding the continued use of marginal correctly in context?
When I buy food, the marginal cost of a bite from the food is very close to the average cost of a bite, because if I eat 5% more food this week, I have to buy 5% more food next week.
Contrast this with the case of listening to music on my stereo: if I listen to 5% more music on the stereo, I don't have to buy 5% more music, and I don't have to replace the stereo 5% sooner. The marginal cost is near zero: just the small amount of electricity the stereo uses, plus a tiny amount of wear and tear. Maybe I only listen to music three hours a week and the stereo cost me $313 and lasts for 20 years, so the average cost per hour is $0.10. But the marginal cost of listening for an additional hour this week is much lower than that.
Utility-scale batteries are more like the stereo than the food.
Assuming you have an endless supply of food but can only take one bite per day and it means tomorrows bite will be a bit smaller.
These storage systems are generally warrantied as 5000-10000 cycles with 85% capacity remaining in 20 years time.
Guaranteed money today is better than saving a few cycles to maybe make money in 20 years time. Now also factor in discounting the risk etc. and the calculation is given.
But the business case is of course calculated on having the entire construction cost be amortized with profit over a chosen period. With some days making more money than other.
What batteries do are extending the time renewables flood the grid with cheap electricity and thus force nuclear reactors to throttle down, gas peakers to shut down etc.
Or these thermal plants can bid negative ensuring they don’t have to turn off while hurrying on their own demise.
Okay, I can follow that. I've noticed on electricitymaps.com that, for Germany, the coal component never disappears, no matter if you have optimal wind+solar conditions near the summer solstice and prices are far into the negatives. Apparently it's cheaper to let it run the power plant at negative prices for days, than to make it stop burning coal for those days. That renewables with storage would make that finally go away stands to reason
But that fully relies on storage. The person you were responding to was asking whether small-scale solar panels make sense. As it is, during those hours where your solar panel is most effective, you can sign up to receive money for drawing electricity from the grid (if prices are negative enough that it outbids even the transportation costs and taxes). Having a solar panel at that time... you might as well turn it off and get a price that's better than free. Storage would be what we need much more urgently than an extra 800Wp solar per household, then we could already turn off those coal plants for probably weeks at a time during summer
> 3) (medium term) The world-conquering dream is for our PV-based steam to replace fossil-generated steam at conventional power plants. That will let us feed electricity back into the grid using otherwise stranded generating assets (e.g. a coal plant). You might see this as a way to combine an existing, uncompetitive coal plant with thermal energy storage and captive renewables to give it economics more similar to a natural gas power plant.
See also: "Thermal Energy Storage in Dirt for Repowering Decommissioned Coal Plants" (although I believe this assumes the storage is using power from the grid):
While I think what Standard Thermal is doing is very interesting, and in particular may be very helpful for already-built thermal plants, I don't think they've solved the fundamental problem that large heat engines are really expensive to build compared to solar.
As I understand it, their market is dependent on it. They can't store electrical energy, only thermal energy, and their system is designed to store it at fairly high temperatures (they don't say explicitly, but I'm guessing 800° and up from the problems they report having to solve) which you can avoid doing if you're just targeting the process heat market. So turning their stored heat back into electrical energy is necessary for their process to make sense, and that requires a heat engine, such as a steam turbine.
But utility-scale steam circuits cost more per watt than solar panels, and much more than batteries, the electrochemical kind.
No, their market is not dependent on it. Generation of power from stored thermal energy is significantly different from directly using solar: it is completely dispatchable. As such, it serves a role even in a situation where most solar energy (or most solar + wind) is used directly. It enables solar to be used in places, like at high latitudes, where it is otherwise strongly disadvantaged by seasonality (something batteries cannot fix).
Long term storage of this kind reduces the overall cost of providing steady solar/wind output in Europe by half.
They are also addressing markets where the need is for heat. If you are going to make heat from the solar energy, storing it as heat is much cheaper than storing it beforehand as electrical energy and then converting it to heat later.
Generally speaking, steam circuits have large thermal masses, resulting in ramp-up times measured in hours, so most thermal energy is nowhere close to "completely dispatchable". Completely dispatchable thermal power is internal combustion engines (diesel or Otto) and open-cycle gas turbines, and Standard Thermal is not targeting temperatures high enough to operate those machines. Adding Standard Thermal to a baseload coal plant will not make it dispatchable; you will still have a baseload plant, not a peaker. It just won't consume coal.
I agree that it would make solar usable in situations where it would not otherwise be usable, and high latitudes are a good candidate.
For reasons like these I do not think that they will result in a cost reduction.
Standard Thermal has been bending over backwards to store their heat at the high temperatures I mentioned, resulting in a lot of engineering challenges that a lower-temperature thermal store (say, 400° or below) wouldn't have to deal with.
For the most part, process heat is lower in temperature than 400°, so I think that isn't their market either.
Batteries would handle the higher frequency components of the supply-demand mismatch curve, so steam sources wouldn't have to dispatch faster than on an hours timescale.
Typically ramping a coal plant up or down only takes a day or so, so if the prices stay negative for entire days, probably there's some kind of perverse incentive where the coal plant operator is getting paid to run the plant by someone else who is also having to pay a consumer to consume the energy generated.
