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Comment by burkaman | Hacker News Reader

Here's the product datasheet: https://www.dyaqua.it/invisiblesolar/_en/documents/rooftile-...

An independent research center lists the efficiency as 0.111: https://integratedpv.eurac.edu/en/products/modules/invisible...

Anybody know how that compares to an average panel on the market today? From a quick search it seems like the best you can actually buy is 0.22 efficiency.

Edit: The best available on this site is 0.216 (https://integratedpv.eurac.edu/en/products/modules/fu-425-m-...), but I think they only test Italian-manufactured products. 0.111 is on the low end, but significantly better than a few things like solar glass.

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That's fine, they look great. Realizing we've got stuff looking like that that generates freakin' electricity is amazing.

Given the poorer efficiency, wouldn't it be better use of limited money and resources to put regular tiles on houses and normal solar panels somewhere else?

(Honest question. I've always wondered why residential rooftop solar, especially since it's usually government subsidized, makes sense anywhere in the world.)

"I've always wondered why residential rooftop solar, especially since it's usually government subsidized, makes sense anywhere in the world."

Transmission isn't free and the surface is already there.

Both places are fine.

Land tends to be expensive; it would be a real challenge in Europe to find somewhere that isn't being used already for some economic purpose, and also isn't a conservation area and/or physically inacessible or difficult to build on.

Adding to the great points already here, decentralized production makes the system more robust to accidents, terrorism, and war. Not immune by any stretch, but more robust.

It's an historical site. The whole point of these tiles is that they visually fit in with the ruins.

These are not tiles you would use for general solar production.

It's an active volcano, you need to run power lines, the ground shifts, and it can blow any time.

It makes sense to make your own power for yourself and you can sell it back to the grid.

I mean if you own multiple properties, sure...

But if it is your house and you don't want to compromise on look, it's a way.

It makes sense to put nicer looking tiles on rooftops if you value the looks of them. You would then find normal looking tiles a tax. That‘s why it could make sense to put solar panels on roofs that don‘t impose this tax on you even if their efficiency is lower.

This answer is to "given that you want solar panels, why put tiles". I think the question is "given that you want tiles, why put solar panels".

Why not both? SolarCity (now Tesla) had solar panels that looks like roof tiles. There's a lot of roof space in any town, it makes sense to use that instead of use up land (that could be used for housing or agriculture) for solar power generation.

But it can be all of the above, too. More energy produced is not going to go to waste, and there's plenty of unusable areas like deserts where solar electricity can be generated in various ways.

Money is being optimized if the land is not free. Solar panels are relatively inexpensive even if inefficient if the land is sufficiently expensive. Electricity cost can vary a lot. If you have a lot of expensive panels and don't have to hook up to the grid that can save a lot of money

A properly designed house with solar can be energy neutral over the year in the UK (not notable for its sunny climate).

What does energy neutral mean? What does properly designed mean? And at what cost to comfort or the property? You could turn off all your electricity and heat yourself with kerosene and have used no electricity for the year.

Usually means "passivehaus", and "energy neutral" would mean "generates an equal quantity of electricity to that consumed, when summed over the year".

> heat yourself with kerosene

That's not energy neutral, is it now, unless you have a kerosene well on the property.

Precisely - for a smallish 120sqm house the passivhaus heat demand is 1800kWh. 3000kWh is not unreasonable for additional electricity consumption. With a heat pump that heat demand should pessimistically translate into <1000kWh electricity, giving us a total energy usage of ~4000kWh. That's about what a medium size (~20sqm) south-facing roof-mounted PV installation would achieve in the south of the UK.

Geothermal energy would be amazing! But it's hard to balance with carbon emissions.

It's useful for the NIMBYs and historical conservation areas.

I mean, not wanting commercial solar farms in your back yard seems like one of the more reasonable things to not want in your back yard. Especially when aesthetically pleasing (if less efficient) rooftop solar fits the bill nicely.

Yeah, but they are also crazy expensive. From their website is 7k Euros for 1kW of installed capacity (not sure if the price includes then installation). I understand beauty factor, but damn. For Pompei it's perfect though

I have worked in the solar industry. As a reference, the average efficiency of "normal" solar panels is around 16% today.

People, including me were installing panels like crazy last year. They are all 20%+, upto 22-something and did cost me 176€ a piece (that includes VAT).

Does that mean that in high intensity regions you'd need active cooling or is that not a problem?

This doesn't answer your question, but I really wish someone would offer off-the-shelf panels with tubing on the back to hook up water lines. It would be dope to cool my panels and preheat my hot water at the same time.

They are usually called "hybrid solar panels" and not exactly a new thing.

Usually cheaper to just put more panels tho. Pretty handy if you need to get the most out of roof space but otherwise more panels + heat pump water heater is much simpler solution.

There's one combining a heat exchanger and photovoltaics: https://triplesolar.eu/en/introduction/

> The front side of the PVT heat pump panel is similar to a solar panel and has solar cells to generate electricity. The backside is a heat exchanger that supplies the energy source for the heat pump. The heat exchanger-collector collects energy form the ambient temperature and additionally from daylight and sunlight.

Not sure how it does throughout the whole season.

They exist! For example: https://www.todoensolar.com/epages/61987244.mobile/en_GB/?Ob...

"Rad" more than "dope" :)

I've seen a DIY system where the panels are boxed in, and the hot air created behind the panels used for blown air / heat recovery heating.

So for those not in the know, fun fact, solar panels work better when they don't get hot. So things like airflow for passive cooling do matter.

I'm aware of several large-scale solar situated in hot regions with no active cooling, so I guess my answer to your question is no, high effeciency panels in hot environments do not need active cooling.

Roof tiles are a different question. There's no airflow underneath them. So they probably get hot. Hot enough to matter? That's hard to say. Do they have the same thermal properties as a regular tile? What is the impact on building temperature? These would be factors to consider during construction. More insulation, better airflow, and do on.

Incidentally since they are not flat (at least not in the picture) that likely accounts for the lower effeciency).

According to some testing, it matters:

https://youtu.be/Mt9qLRN7JvA

FWIW, the way roofs are designed these days (at least over here in Belgium) there is supposed to be a little bit of airflow underneath your roof, which is achieved by letting the ridge and hip tiles hover over the roof (instead of cementing them like they used to do) and putting a perforated grate at the bottom just above the gutters instead of boarding it up.

Would one be able to extract energy out of the hot tiles as electricity? With a heat exchanger?

Where would you put the cold side?

Fun fact: resistance sucks and makes your electrons bump into protons and crash causing waste heat. Super conductors are usually supercooled and have 0 resistance and every electronic works more efficiently cooler.

> resistance sucks and makes your electrons bump into protons

This is a myth with little bearing to reality. Protons (and the atomic nucleus) are insignificantly tiny when compared to the size of an atom. The major contributor to electrical resistance are defects to the crytal lattice of metals and grain boundaries.

Don't you need the defects to have semi conductors? I seen some really cool experiments with superconductors and every computer works better cold. Isn't that why Google's quantum computer is supercooled?

> Don't you need the defects to have semi conductors?

No. However, most of the time you want doped semiconductors and doing that introduces defects. The defects are bad for resistive losses but that's life.

> every computer works better cold

No. Conventional electronics based on doped semiconductors don't work below a certain temperature because the impurities are "frozen". There is a sweet spot of temperatures that works best. The purpose of cooling on a computer is to keep the temperature as close to the sweet spot as possible.

> Isn't that why Google's quantum computer is supercooled?

Quantum computers like Google's rely on superconducting materials (most of) those require sub-Kelvin temperatures to work, both to reach the superconducting regime and to reduce phonon induced decoherence. Superconductivity works in quite a different way to conventional materials to conductivity in semiconductors and metals too.

The temperature coefficient of resistance is real, though, and could do with an explanation that isn't too quantum.

Of course it is! And the explanation isn't even too quantum. Heat induces atoms to vibrate, these vibrations mess up with the perfectly periodic potential that you would have at 0 K and induces electron scattering which leads to more electrical resistance.

I believe Longi sell a 22.8% module. Individual cells run 26%.

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