Super Simple Solar Energy

PWM is a super-simple way to turn a fixed load resistor into a variable resistor, but I agree that a linear regulator would be fine, because the lost heat in the big heat sinks would be part of the air-heating purpose.

But I don't agree that one can count on eking out the last 10% with MPPT. Before settling on my simple scheme, I purchased eval boards for five different MPPT chips. My experiences with them soured me on the concept of getting the last 5, 10 or 15%, over the wide range of solar conditions one encounters. I'd say probably the only way to succeed in that is to be creative with hardware, and to write some refined software to control it. I do hope the MPPT code in my roof's micro-inverters does that.

But even MPPT that misses perfection by 10% is awesome, because with poor MPPT, or none at all, we will suffer up to 90% losses.

As for my other claim, that the sky's variability is so great, that it's not even worth trying for the last 10%, look at plots of 9 successive days of detailed data from my roof. Even the best days suffered dips, and as for the rest of them, forget it. With this type of variability, it's a challenge to even properly evaluate an MPPT algorithm, operating in situ.

BTW, my simple scheme worked particularly well in poor weather, managing add battery charge even under dark rainy conditions. Some schemes may do well in the range of 50 to 100% of maximum, but the plots show how that can be a small fraction of the time.

I did a MPPT for the ESA Rosetta deep space mission, we had better than 1% deviation from the maximum power point

I invented a circuit to get that accuracy even with high solar array capacitance, which normally is a big problem for fast MPPT action

Cheers

Klaus

And efficiency counts

If you gain 10%, you can effectively reduce your investment by a lot of money

If the MPPT has slow reaction, you can loose a lot more than 10%

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some half truths there

There's a place where making an investment is worthwhile.

In our design, the cost was very low. Significant below 1USD

nd Solar Collectors are one example of this. Seems like a good project, bu t it also seems like a bunch of work. So another idea is using solar panel s in a super simple way. Not to replace electricity, but to provide a litt le heat to the basement. So it would just be solar panels connected to a r esistive load. No battery storage, no inverter, no temperature control.

ells for about $100. So could make 4 panels , 2 feet by 3 feet to hold 24 solar cells on each panel. Maybe run lines for each panel to the basement .

I'm sure there are lots of ways to do this job more efficiently, but really ? You want the guy to run plumbing instead of wires for a 300 watt heater?

I seem to remember that you gave us some details about this, but checking in my Klaus Kragelund folder, where I've saved quite a bit of other stuff, there's nothing about MPPT.

I can attest to the practicality of heat pumps. When we were replacing our HVAC system a few years ago, it was pointed out that purchasing a heat pump, instead of a simple compressor, would cost only a few hundred dollars more. Now whenever the outside temp is 40F or above, all our home heating is done with the heat pump. It draws 5kW when running, and heats at about half the rate of our oil furnace (the air-duct blower runs more slowly in the heat-pump mode). I'm a heatpump fan.

:-)

It was in this thread:

And this was the comment:

I am not allowed to tell you exactly how it works, but I will try to see if I can find someone doing something similar, and post that

Cheers

Klaus

Ha, it is actually shown in a document from Terma, VERY close to the actual circuit:

I remembered incorrectly, it was not 99%, but minimum 99.7% MPPT point tracking requirement

AFAIR is was tracking at 100Hz

The superbuck converter is also shown

Cheers

Klaus

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But NT doesn't know, and can't tell us, which bits are less than perfectly accurate.

I can't find anything wrong with either statement, so this looks more like NT not understanding what is being said and.

Dehumidifiers do cool the incoming air below it's dew point. The cold, dry air is then passed over the other end of the heat-pump circuit to warm it up again (and recondense the refrigerant that little bit faster).

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y accurate.

Sure I can. And for once I will reply despite your childishness.

e NT not understanding what is being said and.

ry air is then passed over the other end of the heat-pump circuit to warm i t up again (and recondense the refrigerant that little bit faster).

Heating air doesn't directly change its moisture content, though it does lo wer its RH. But heated indoor air inevitably exchanges with outdoor air in domestic properties, which is on average lower in moisture content, and whi ch then drops RH as it warms. Exchange between heated indoor air & unheated outdoor air is the mechanism by which the great majority of houses are deh umidified.

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Not really, on both counts there are other options too. Desiccant wheel deh umidifiers don't use chilling at all. Nor do box-of-salt type ones, even th ough they're of minimal use.

I know from Bill's history here that any moment of sense from him is merely an invitation to enter into his spiral of madness. I'm not interested in d oing so & don't care what he has to say.

NT

Where is this that basement walls are a magic 55F? I know in Vermont, the frost line can get down to at least 7'. ...and yes, in much of the country basement walls *are* insulated if it's finished living space.

Where does this magic 55F dirt come from?

Heat exchanger? I'd think an expansion tank would be needed in any case.

It finds the maximum power point within 0.3%, but the losses of the DC-DC converter are up to 5%. To maximise the output power, it might have been worthwhile putting more effort into the latter and less into the former.

I once worked on a system where bypassing the MPPT DC-DC converter greatly increased the efficiency, because the maximum power point of the solar panel matched the battery voltage well under normal conditions, and the MPPT was not very efficient and had awful dynamic behaviour.

y are close to the optimum temperature. Only above ground walls are insula ted.

nt

ent

That's the issue. Most basements aren't insulated because they are not liv ing spaces and they are not heated. If they are, then they are generally in sulated in colder climates.

d to be cooled if they don't have a path for the internally generated heat to escape. Don't try to compare an insulated wall with a huge thermal hole in it (windows) to a basement wall. Temps inside don't really need heat u

ned, it is the dampness of basements that gets to you more.

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efficient. And plumbing solar collectors is a lot more work. Here ( Dela ware ) you either have to drain the system at night so it does not freeze or have an expansion tank to so you can use antifreeze .

Idk anywhere that code allows a heating water system to be connected to the potable water system without a backflow preventer. Which means you need an expansion tank anyway.

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So NT agrees that this statement was entirely correct

This is just irrelevant carping. Out-door air was be wetter or drier than indoor air, or warmer or cooler. Swapping air with the outside world is ventilation.

It's an incidental feature of the more general process of ventilation. If you are getting worried by damp patches on the walls, dehumidifiers attack the problem directly. NT is in evasive mode here.

I have seen both sorts of dehumidifier sold for domestic use. It's nuts, but some hardware stores cater for people with little money and even less sense. As NT admits, they don't work well enough to be of much use, and they certainly aren't cost effective.

Laboratory desiccators frequently used water absorbers which can be regenerated by heating, but strictly for tiny volumes of air.

There's no madness involved, if we exclude NT's inane enthusiasm for unhelpful pontification.