Improve the performance of a solar heater

One day I started thinking about how to improve the performance of my solar heater even more.
Surely, good things can always be improved a little.

I was also worried about using a pump all day long.
Sometimes the times were very long, and it made me think. It seemed that I was not cooling the collector efficiently.
I also had to deal with the issue of measuring and optimizing the flow rate. And how to adjust the speed so that the system achieves the best temperature.

Pumping efficiency

This last point is quite delicate.

To take advantage of the plates and their energy efficiency, we have to think about «cooling the plate»

Why? Because heating the tank and cooling the collector plate are completely synonymous.

If the pump circulates, and the collector stays very hot, we are sure that something is not going very well.

It is quite likely that the collector has internal dirt.

It could also be that the water circulation is very fast.

When the circulation is very fast, the water that remains in the collector's path for a short time.

This prevents the water from extracting enough heat from the tubes of the hot collector.

And what happens in this case is that the heat obtained from the sun is greater or similar, cooling power of our circulating water.

It's like... wanting to buy tobacco from a vending machine, without getting out or stopping the car.

Calculating the optimal speed of circulation

This is the problem, and below I present a simple solution, and it will be the definitive solution to improve the performance of the solar heater, quickly, efficiently, and super economically.

But let's first meditate on the effects of this mismatch in the flow rate.

To make sure we understand what we are doing.

To finally realize how we are going to improve the performance of the solar heater by understanding the problem.

The speed of water flow takes or leaves so much temperature depending on its speed of passage, it may not seem that it is something critical, but it can raise or lower the tank by more than 10ºC at the end of the day.

To better understand and analyze system performance, we are NOT going to think about «heating water».

Because that really doesn't tell me anything, the water can also be heated sooner or later due to other circumstances (climate, consumption)

I'm going to base myself and look at the cooling of the plate.

Obviously we already know that, if the plate with the collector is at a high temperature and it doesn't go down, it means that we are not cooling the collector, that would be poor performance.

It is almost always given away by the intense use of the pump.

Inefficiency due to slow circulation

If the collector does not lower its temperature, it may be significant that the water is circulating very slowly, that means that the heating by the sun is much faster than the cooling by the water that passes through.

We can find out by increasing the speed, either by configuring the pump, or by adding another booster.

Inefficiency due to rapid circulation

Although it may also be significant that the water is circulating so quickly, that it leaves the collector much sooner than expected, and has not been able to extract that energy Thermal.

This 2nd case is usually more likely, and is worse than the 1st.

Worse because we can generate wear due to friction and we are punishing the pump to do a bad job and with little efficiency.

Intermittent energy

To understand this situation, we can consider the example of a hand passing over a candle, or a hand passing over a barbecue.

Passing your hand over a barbecue

Who hasn't passed a hand over the embers of a barbecue in winter to take advantage of the residual energy and experience the free comfort?

We also removed it quickly, eh? LOL

But what would happen if we passed it over just once and too quickly? that we hardly notice.

This is what would happen in a very fast circulation, that the water that enters the collector would come out without having taken hardly any heat energy.

Our instinct realizes that the sensation is pleasant if we put and remove our hand intermittently and quickly.

What we cannot regulate in power, we regulate in intermittent exposure.

Other forms of intermittent energy efficiency

This is how microwaves and induction cookers actually work.
And although it is not very relevant, I will tell you that high-power LEDs also work in a similar way, with a high voltage that would melt them, but since it is an intermittent current, we perceive the light explosion but the component is not damaged.

Who has not ever played by passing their hand or a finger over a candle or a lighter?

The same situation, we can pass a finger over the candle infinite times. If we do it fast enough.

We apply this understanding of intermittent energy in our pump

To cool our collector (which is directly proportional to obtaining the maximum temperature for our water tank), and improve the performance of the solar heater, we must think and understand this.

Only in the case that it is a matter of inefficiency due to excessive speed.

How can we make the water stay longer in the collector, if ours is a fierce pump without a power regulator?

CHANGING THE CONCEPT OF SPEED CONTROL BY INTERMITTENT FLOW

That is my idea, and it is not just a I'm not just talking about theory, but I applied it to my own system, and I achieved much higher temperatures and my water pump works at 50% or maybe less

I can't make an exact calculation, because even though I apply 50/50 times, the cycles have also become noticeably shorter, as the plates cool down faster.

So what is intermittent circulation flow?

Well, as the name suggests, it is a technique that I have applied based on this overwhelming theory.

We only have to be responsible for the pump not becoming a crazy woman dancing, because it could be damaged.

Reasonable times can be 10″ on and 10″ off, 20″ on and 12″ off. pause, and so on…

This action makes the water that remains at rest during that time, be able to capture more heat energy than when it is circulating.

When it circulates again, the water comes out much hotter.

This new circulatory form will reduce much more the energy that the collector accumulates.

What is the optimal configuration to improve the performance of the solar heater?

Well, each one must determine with several tests.

It all depends on the distances, internal capacity of the collector tubes.

I have configured the ON cycle for 5 seconds, and the OFF cycle for 10 seconds, without doing too many tests, and the difference was noticeable.

We can try and vary it, the important thing is that this method does not need so much precision.

Although it is not the perfect adjustment, it does It will improve the performance of the solar heater immediately from the first second.

If we exceed the pause time, for example, we will simply waste a little time, causing the water to come out of the collector later than it should.

I suppose that the ideal would be, assuming the pumping time as time, the time it takes for all the liters to come out of the collector. The pause is the most important due to the capacity to cool the plate and depending on the season of the year.

Costs and complexity to apply intermittent circulation

Totally ridiculous cost, with little more than 10 euros.

Complexity, from 5 to 30 minutes to interconnect a small circuit between the pump and its feeder.

A small circuit is applied in the electrical supply of the pump, I don't even need to go up to the roof to touch anything in the collector or the tank. I do it in the feeder itself.

Below I explain the necessary circuit and its installation.

Amortization

Oysters!!!!!!!!!!!

From the first day, because we will be consuming less electricity, using the water pump less, and heating our tank more efficiently.

Since the cost is ridiculous, it is equally ridiculous to want to do this calculation.

So normal pumping works

The pumping is constant and tries to capture the energy from the collector, and therefore, cool it (both things are the same)Depending on the speed, it may not be effective in optimally cooling our collector.Sometimes we will not be able to vary the collector's performance due to a water pump where we cannot adjust its speed.

Thus intermittent pumping works

The water flow circulates to transport the water to the tank, and suddenly stops for a few seconds, and then circulates again and repeats the same pause.

Each of these pauses causes the water to absorb a large amount of heat from the collector.

These periods of circulation and pauses are short intervals.

When the paused water finishes its journey and goes outside, it will have been in direct contact with the inside of the collectors for a long time and its temperature will be much higher.

Another added advantage, and no less important, is that the pump needs less operating time, and if we do it right and this performance is good, the differential thermostat will send fewer stages to exchange the temperatures between plates and tank.

The reason for this last effect is because the coil cools down much sooner, and cools down much more.

Therefore, it will take longer to heat up again and request another new stage of exchange.

and finally…

Install the circuit to convert water circulation into intermittent circulation.

The circuit is very simple and without mysteries, it is a timer circuit with 2 potentiometers and a relay.

The 2 potentiometers are 2 instruments that are turned from one side to the other.

Potenciometer is what we used to have in the old devices to lower or raise the volume of the radio.

The relay is an electrical instrument that acts as a controlled switch, when the circuit closes the relay it is as if it activated a switch, and vice versa.

This circuit can be bought ready-made in many electronics stores, they are sold for learning purposes.

We can also make it ourselves at home, or by asking someone knowledgeable on the subject for help.

The circuit is the photo below, they are sold in electronics stores.

They are demonstrative assemblies for learning applications.

Approximate cost, between 5 to 10€