I have heard some salespeople vigorously defend the heat pump as a solar hot water system. It does use the heat (or warmth) of the air to heat water. The source of that heat is the sun. Therefore it can be seen as a solar hot water system.
But there are no collectors involved and it does need electricity to function. Far less than any electric hot water system though. That is the reason that it receives a Federal Government rebate and renewable energy certificates (RECs).
Heat pump advantages
The biggest advantage: no direct sunlight is necessary. We also recommend a heat pump where a solar hot water system is not feasible (e.g. for properties with an asbestos roof, when the north facing roof space is too far from where the water is to be used and of course where there is a lack of sunshine).
Heat pump disadvantages
The disadvantage: while producing hot water, it makes a noise (similar to an air conditioning unit). It is therefore best to put it away from any living areas. Electricity is necessary to power the fan that draws in air. This is minimal compared to an electric hot water system.
I find it interesting how there are hundreds of articles about various industries that will “suffer” from the Carbon Emission Scheme. Yet there is only this tiny little mention of how it will affect our daily lives.
Having to pay twice as much for electricity sounds outrageous at firt. However, that is only the case, if we do not change our behaviour. And that is exactly the point of the emission scheme:
Changing behaviour from the wasteful use of non-renewable resources with its attached pollution.
So I really welcome the increase in costs and hope that it will spurn many new solutions that can be offered to the market and will enjoy a quick uptake.
It is easy to get overwhelmed by the choices. However there are some simple things to consider to find the best solar hot water panels for your situation.
Panel Size
Most panels are about 1×2m. Depending on the tank size, you will need between 1 and 3 solar water panels. Usually a system comes with the right number of panels and any installer will always make sure that they are adequate for your situation.
If you have an existing solar hot water system that does not generate enough hot water, you might want to look into getting an additional panel. It is best to go back to whoever sold you the system, to make sure all the fittings go together.
Technology
There are two major technologies to choose from: flat plate and evacuated tube.
Flat plate technology has been around the longest and is the most widely used. The glass is sturdy and they usually get a slightly higher REC rating than the evacuated tube system.
Evacuated tubes have two advantages: they produce a little more heat when there is no sun and in cooler climates and they are not prone to frost damage. The drawback: tubes break more easily (but can be replaced individually), in summer they might be too efficient, which leads to wasted water and they are more expensive.
We have chosen flat panel technology, because for the hot climate in Queensland they give a better return on investment. In colder areas, the tube technology certainly has its place. See solar water panel system differences.
Casing
Yesterday, we replaced a solar hot water system where the panel casing had rusted away. To prevent that for our clients, our panel casing is aluminium. The corrosive layer that forms has the same silvery look and more importantly prevents all further disintegration.
Many panels are made of zincalume. It is coated steel (the coat is made of zinc and aluminium). As soon as the coat is broken at any point (corrosion or any scratch might do that), it will start to rust.
Frost Tolerance
When water freezes, it expands and thus might crack the panels under heavy frost. There are two ways to prevent that: Frost valves and closed-loop systems.
With a closed-loop system, it is glycol that gets heated up in the panels. It is transferred in a heat exchanger to heat the water. Glycol does not freeze, even in below zero temperatures. These systems are more expensive.
When you only experience the occasional frost, frost valves are a good alternative. As temperatures drop, they open up so that the water drains out of the panels. That way, they damage is averted. Please note that some frost valves include the manufacturer’s warranty against frost damage, whereas others don’t.
How do Solar Water Panels Work?
Here is John, our plumber explaining it.
Conclusion
It is good to know about these things, when you talk to salespeople. It means you can ask the right questions. When you go through the free instant online quoting process, you’ll find that the ideal system is chosen, so that you can be certain to get a high quality long-lasting solar water product that keeps producing you hot water.
Water heated by a solar water heater can reach temperatures of up to 90 degrees Celsius. To prevent accidental scolding, we are putting in a tempering valve.
It automatically mixes the hot water with cold water to reach 50 degrees Celsius. So in effect any hot water tap has 50 degree Water coming out of it. It is hot enough to want to mix it with cold water before having a shower. But it will not burn anyone.
The tempering valve works mechanically. The valve inside expands and contracts depending on how hot the water is that comes through. When it expands, it lets less hot water pass and instead adds cold water. The opposite happens as the hot water flows through loses heat: the valve contracts and therefore opens up more of the hot water stream. Out comes the 50 degree Water.
Every solar hot water system comes with a booster for the times when there is not enough sun. There are two types of booster technology: electric and gas.
Electric Solar Hot Water Booster
This is the most common way to boost your water heating. It is the most economical as it does not have a large upfront cost. When you start using your solar hot water system, it is best to leave your booster off until you run out of hot water.
Once you know how many days of clouds that takes (for us it is 3, but that will be different for every family, depending on how you use your water), you can turn the booster on before the water goes cold. But it is worth testing it out first.
Is it not Automatic?
The electric booster has a thermostat that only lets it start when the water temperature falls under 60 degrees Celsius. So you could just leave it on and forget about it. However, that would result in wasted energy.
Let us assume that your whole family has a shower early in the morning. The temperature in the tank drops to 55 degrees. That would trigger the booster to heat the water. However an hour later, the sun hits the panels and would have heated the water far more efficiently and cheaper.
It is therefore best to leave the booster off and only turn it on when you really need it.
Which Tariff?
The official government suggestion is to connect the electric booster to Tariff 33. That is the off-peak tariff, which means it only runs for 18 hours a day. It is cheaper than normal electricity, but in many situations you use far less electricity than the minimum payments.
(Over 3 years, we had our solar hot water connected to night tariff. In that time, we used a total of 177 kWh for the booster. On Tariff 11, we would have paid about $30. Because of the minimum quarterly payment to have access to the night tariff, we paid $120 in that time.)
The story is different if you have something else connected to the off-peak or night tariff (e.g. a pool pump). Then it might be the best financial choice.
Gas Boosted Solar Hot Water System
The other booster uses gas. Even though the greenhouse gas savings are slightly higher with this type of system, you basically have to purchase two hot water systems (one solar and one instantaneous gas heater) which are coupled together.
As long as the water heated by the sun is hot enough, it just flows through the instantaneous gas system. When the temperature drops below the thermostat setting (usually between 45 and 49 degrees) the gas system starts heating.
In some instances it is possible to use an existing instantaneous gas system.
SolarPay News Feed
