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Comment by nsxwolf | Hacker News Reader

I love the idea of reclaiming some of the energy from our lighting. Perhaps one day solar cell wall paints will be a thing.

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If those solar cells are efficient, then they'll look you've painted the walls black. Not only will the quality of the light become worse (harsher shadows from less diffuse light), you'll probably install more light bulbs to compensate.

Exactly. Now that we're putting out primarily visible light from our bulbs, there isn't a bunch of free energy floating around there. Far better to save the energy by making the bulb as efficient as possible in the first place than to try to capture it back.

Technically speaking the solar panel walls would get most of their output from the daylight, assuming you have windows, considering that it's thousand times more intense than light bulbs.

But yeah, I wouldn't want to live in black glass coated rooms.

Ha, yeah, but that's kind of like putting your jacket on under your clothes.

The EU incidentally created a similar problem when banning most incandescent bulbs.

Well, at least in some countries. Here in Norway, most buildings are heated by electricity - so replacing incandescents with LED or fluorescent bulbs effectively means that you spend less on lighting, more on heating and the sum stays the same - except the new bulbs are costlier and (mostly) provide less comfy light.

Sigh. Free lunches remain elusive.

Using electricity for heating is a terrible idea. Unless you are a rich country like Norway which can afford it.

You would be much better using LED for lighting and gas burning for heating.

So the sum does not remain the same if you do things properly.

Considering practically all of electricity production in Norway is renewable (99% hydro) the less efficiency in electrical heating can be traded off the more efficient but CO2 emitting gas burning.

It's true though that in countries where there's a significant fossil dependent electrical sector it's better to burn the fuel directly.

Except it is not as cold everyday, and not every room has the light and heating demands perfectly proportional. And incandescent bulbs also generates more trash.

Tying lighting to heating is inherently inefficient.

Wasting electricity like that... At least put it through some computer before throwing it away as heat.

Heat pumps are way more efficient than just resistive heating.

How is that possible?

They steal heat from outside. It takes less energy to move heat from a cold place to a warm place, than to create warmth "from scratch".

A heat pump extracts thermal energy from, say, air. Electricity is not converted into heat, but used to create a temperature difference (one part of the system gets colder, the other gets hotter). This is vastly more efficient than using resistive heating elements. Such a system can appear to be more than 100% (up to around 400% [1]) efficient, if you look at the electricity going in, and the heat coming out.

[1] https://en.wikipedia.org/wiki/Heat_pump

I don't think they are more efficient in Norway harsh winters..

That's actually a reasonable point, and it may be true. There's got to some temperature delta makes a heat pump a losing proposition, but I'm not sure how big that threshold is.

I accidentally replaced one of my heat pumps with an A/C only unit. So now I have to run the emergency heat strip all winter. I haven't seen any real increase in my power usage. The heat strip was running most of the time anyway because of low temps.

Recent winter pumps work pretty well down to -20C, and don't get any worse than resistive heating after that.

In the north of Norway, Tromso, the lowest monthly average temperature is -6C for January. Coastal Norway is surprisingly warm due to the ocean and Gulf stream.

Good point. Maybe things that are frequently dark - like baseboard trim?

A bit like a perpetuum mobile, right, light is captured by the walls which generate electricity for the lights. Free lighting for everyone...

Well the point of lighting a room is that you want the room `light` and making walls that absorb light makes them not reflect light and then your room is dark again.

So even if this was possible (which it is not), the idea would still be rather useless (until you managed to achieve efficiency over 100 % ;) ).

It's more efficient to wear night vision attire everywhere. Why illuminate a whole room when you only care about the light that makes it onto your retinas?

If we paint the outside it might make sense. As long as you like black houses.

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