captainflack

Heat pumps are definitely more efficient, but how much depends on a number of factors.

We use our aircons for some heating in winter; my parents in the next street have a newer bungalow and they have built in big aircon units which is now their sole heating. They have walls and roof insulated, it works well.

Main problem is as outside temperature approaches zero, the cold side of the heat pump drops below zero (it has to be colder than the air temp in order to transfer the heat). That means you get condensation freezing on the coil, which reduces performance. So it has to go into de-icing cycles to heat the coil and get rid of ice. Below zero, this doesn't happen, as any water in the air will already have been largely condensed and frozen out, the issue is mainly in the few degrees above freezing, which is typically the kind of coldest temps we get in Portugal when you really want the heat.

The performane factor can be quite significant, with ideal conditions you can get 3-4kw of heat for only 1kw of input electricity. So three or four times what you'd get if you just burn the electricity through a heating element (which will give you basically 1kw). It sounds like a perpetual motion, but it doesn't violate any thermodynamic laws (not a closed system, it is using the electricity to transport in heat from outside to inside).

liveaboard

yes; the times a heatpump can make a lot of heat is when you don't need much heat.
They make noise, they're complex and expensive.
When solar pv costs so little, I think (the actual math needs real numbers that are hard to find) that IF you're using self produced solar electricity, it will be cheaper to use more panels and a resistance heater than fewer panels and a heat pump.
IF you have a place to put them (most people do not).
Of course that turns around on days (and nights) when you're forced to buy power from the grid (after feeding it in all day unpaid).
A large water heat store tank might be able to bridge overnight, but even 2 days of heat store is a real challenge. the loss through insulation adds up and takes away the fun.
In Portuguese, "Inercial Acumulador" returns many possibilities.
There are other technologies I've read about, but it seems they don't work out economically because I don't find them available for sale.

I heard that one provider, energia simples, will pay a feed-in tariff; I filled in their form but they don't reply.
So I went through the websites of all the providers; what a load of repetitive greenwash!
They all say they're working for zero carbon, blah blah blah, but all they want to do is sell power that they buy from the cheapest source.
Guess what kind that is?
And they all expect to have your excess solar electricity for free.

Midgo

I've been thinking ...
Surely, here where Summer is so hot it would pay to fix the elevation angle at the winter optimum?
In summer we have more than enough sun, maybe too much

Score76

This set up works well. Renusol Console+ bases, during summer the panels sit flat into the bases and are at 15 degrees. In the autumn I add the 50cm legs (simple process, 2 bolts with wing nuts) which jacks the panels up to 35 degrees. Remove again in the spring.

macliam

Neat idea, but that looks more like 45 degrees.... and, of course, PV panels. Where water is concerned,even 45 degrees would still be less than optimum for Winter and 15 degrees too flat for Summer (let alone all the faff with flexible couplings).......

PS, what's the lif expectancy on the boxes? With me, even a "UV stabilised" Keter shed lasted less than 10 years before becoming brittle and cracking up in the sun.

Score76

You can of course make the legs whatever length you like, these were 1m lengths of alu angle which I cut in half to make 2x 50cm.

The bases have a 10yr warranty, and if you think about it, through the summer when the sun is at its strongest they are entirely in shade. They are slightly smaller than the panel which wraps over it. The whole system panels, micro inverters and bases pays for itself in 2 to 3 years as I've detailed in previous threads, so even if a base starts to deteriorate after 10 years you are still quids in (or euros).

liveaboard

Nice, I like it.
It looks like your angle is too flat for winter, but it's hard to tell in the photo.

Score76

For my latitude here in Lagoa the theoretical best angle for winter is 57 degrees, spring/autumn 34 degrees and summer 10. I've just been and measured with the Solar Tilt app and with the legs on gives 37, without 15. Will certainly perform better over the course of the year, and for the 2 euros per 1m length to make them it'll be worth while. Certainly not worth thousands for one of these rotating sun tracker jobs, just buy more panels.