Just been chatting with AGL for a better rate. Stumbled across the option to hook up a thermal storage Space heater on controlled load. This would provide heating at 50% less cost. No idea what they cost to buy yet. So wondering if anyone uses one (how good are they? / is it worth it)? and anyone found a good deal on one?
Heating house with offpeak/ controlled load rate via Thermal storage Space Heater. Anyone crunched the numbers?
tunzafun001 on 15/08/2018 - 13:19
Comments
Gas is pretty bad…
It used to be the case that Usage was a fraction of the bill, now Supply is the fraction of the bill!Gas connection fees are far too high. Though am considering going down the hire a bottle from BOC route.
There is an old ducted reverse cycle system in the roof (old school where the compressor is in the roof). It's loud, and I cant see it being great in summer dissipating the heat back into the roof cavity. Might see about getting a new model compressor on the outside and make use of the ducting.
House has solar elect, and hot water. Interesting the hot water over heats in summer and just purges. Need to make use of that somehow..A steam engine reverse cycle compressor!
Bottled gas is double the street gas cost (where I live anyway) and not viable.
Old RC aircon probably won't be as cost effective. Modern units have a coefficient of performance of 3 or more (some over 5) so they can give a heat output several times their power usage.
If you can find your model's rating you can decide if it is efficient. A radiant bar heat has a COP of 1.
https://en.wikipedia.org/wiki/Coefficient_of_performance
As mentioned above, reverse cycle AC is cheaper to heat with at peak times. Even at colder temperatures they will give around 300% efficiency so it's better than a 50% saving. Slightly higher cost to install a split system but would pay itself off in a couple of years when compared to elec resistance.
How can you have a 300% efficiency? Could use them to produce electricity!
By pumping the heat from one side to another, it can pump 3MJ of heat for the expenditure of 1MJ of energy.
Some Daikin models go over 500%. So you get equivalent heat output to a 5kW heater for 1kW of electricity usage.That makes no sense - violates the laws of physics.
If you got a machine that was better than 1/5 efficient at converting heat to electricity you could spontaneously create electricity where there was none before.
Are you sure you don't mean it is just such a great heater that the 1MJ heater feels like a 5MJ one? Like those new light bulbs that are the equivalent in brightness of the old light bulbs?
@Quantumcat:
Think of it like a refrigerator.
The condenser “pumps” heat out of the inside of the box that then radiates from the coils.
The energy required to run the pump is not dependent on the temps inside or outside the fridge.
In the case of an Reverse cycle air con, the energy required to transfer 3mj of heat for the outside ambient air to the inside air is 1mj.An analogy is a water pump. You don’t think physics is violated because pumping hot water results in more than the energy used by the pump being transferred to the end destination.
@mskeggs:
It would make sense if the outside air was hotter than you wanted and you were just moving it from outside to in. But a heater has to actually heat it, surely? If all it is doing is moving hot air from one place to another it isn't being 500% efficient, that means something else is heating the air (and using energy to do so) and all it is doing is being the messenger. Saying it is 500% efficient is like saying I am earning $1000/hour by taking money out of my partner's wallet. When they're doing the working and all I'm doing is helping myself to it.@Quantumcat:
How does a fridge make the inside colder than the room temperature, the opposite trick?
It truly does concentrate heat from the outside ambient air and move that heat inside, using less energy than heating the air directly.https://jhc.com.au/air-conditioning/reverse-cycle-air-condit…
You are correct that something else is heating the air, it is the sun, but since the energy we supply is just to move the latent heat from the cold outside air, and we get 5 times out for what we put in, it seems 500% efficient.
In your analogy it is like a forest. Nature supplies the fuel, but the logger transports it. If we get more energy out than the logger uses,it is positive EROEI.
@Quantumcat:
mskeggs is correct.RC Air Conditioning is 100% capable of shifting heat energy from one area to another.
It's not generating heat, just moving it.
As a result, it can move more heat energy than the electrical energy it consumes to run the pump.
In doing so, it "cools" the outside air (because heat is removed).
In cooling mode, the AC system "heats" the outside air, pumping the heat from the room to outside.It's a bit like a 70Kg human can move a 1500Kg Vehicle by pushing it. The human isn't creating the vehicle in a new location, just moving it there.
There's no laws of physics being violated.
@scubacoles: I guess I need to do some reading…. But how can the air conditioner heat the house to warmer than the air outside? With your example of the human pushing the vehicle - how can the human move a 500kg vehicle and have it turn into a 1500kg vehicle when it reaches its new destination?
@Quantumcat: I'm going to take a stab here and say it's about volume of air. Perhaps using a couple of degrees from a large volume to make a larger increase over a small volume. Something along that line.
@Quantumcat: air conditioner works based on the principle of vapourised liquid taking heat away with it (same thing you'd see when doing BBQ or refill butane gas lighter, the outgoing pipe get cold and ice build up around it) , so what they did is pressurised the liquid inside the coil and suddenly let them turn into gaseous state, which will quickly cool down the surrounding environment. Electrical energy is used to compress the refrigerant and the refrigerant was selected based on its special ability to quickly turn from liquid to gas when losing pressure)
air conditioner just use one form of energy (electricity) to move refrigerant and change its status between phases, in doing so it inadvertently creating temperature difference between part of the system.
@lgacb08: For that explanation to work for a reverse cycle air conditioner to heat a house, the electrical energy would be used to make the pressure really low so the refrigerant turn from gas to solid and would expel heat - is that what you're saying?
@Quantumcat: it's not actually 300% efficient. It is using the electrical energy supplied from the grid and adding energy from the outside air. When you add these 2 together you get 300% of the electrical energy coming out as heat. Remember the outside air, even at 0°C that is 273 Kelvin. Zero Kelvin is 0 energy so air at 273 K still has plenty of energy that can be used.
@MikeKulls: it isn't 300% efficient, it isn't producing heat. It's moving the air and if you want to talk about efficiency you would talk about how much kinetic or potential energy has been given to the air compared to the electricity used
@Quantumcat: well when you do that you get 300% efficiency. It could use 1000W and output 3000W of heat. I'm not sure what you mean by it is not producing heat, it certainly appear to produce heat :). The reason it can appear to have an efficiency of 300% is that we are not counting the energy it drags from the outside air.
@MikeKulls: 300% efficiency means it is creating energy out of nothing, which is impossible. Efficiency means transferring one kind of energy into another, and how much is lost by doing so. 300% efficiency means you have created energy from nothing. The heat came from the air, not the electricity. The heat can come from the electricity in a normal heater - the electrons travel through a resistor. But not in this one - the electricity is moving the air not creating heat.
Lifting water and dropping it over a water wheel to make it spin = transfer of energy (by lifting the water I am giving it potential energy, dropping it transfers the potential into kinetic, which turns into kinetic energy of the water wheel when it hits it).
Moving a water wheel from out of a waterfall to under a waterfall is NOT a transfer of the energy I spent moving it to making it spin! That energy to make it spin comes from the water falling on it.
In the first case you can see even 100% efficiency is difficult to achieve - it would mean absolutely no molecules could fall away from the wheel or not contribute to its movement, and there could be zero friction to overcome etc.
When air conditioning units are quoted in their efficiency, they are quoting the intended work effect over the required effort to produce it. you have rightfully assumed the wrong interpretation that the efficiency quoted is a zero sum game (more on the language below)
In this situation, the intended effect is "Heating the Room", how do they measure it? Amount of energy expelled into the room. Of course the work required can be calculated as what you use to run the pump and fan units.
Thereby it is possible to have more than 100% in the number, however technically this number is not "efficiency" but "coefficient of performance". It is just used in normal language that it's incorrectly abbreviated to just "efficiency"
In the end the result is the same however, if the system produces 3kw of heating, for only 1kw of electricity used, you are still "winning" because if you use a standard resistance heating element, you would have to actually burn 3kw of electricity to produce 3kw of heating
So actually neither of you are strictly incorrect, it is simply a misunderstanding of the terms being used in your conversation :), you are correctly applying the literal interpretation of what efficiency is whereas the industry has in common language changed the meaning of the word
@Quantumcat: as I said, it is not creating energy out of nothing. It it taking energy from the outside air, adding that to the electrical energy expended and you get the heat output greater than the electrical energy.
To go with your water analogy, imagine you have an extinct volcano full of water. You need to pump the water up 100m but once you do it can fall 300m. You've pumped only 100m of head but you can gain energy with a generator at the bottom of 300m head. You've used electrical energy to unlock potential energy in the water. It's not 300% efficient as the rest of the energy has come from somewhere but it appears to be 300% efficient
@Quantumcat: I should add the electrical energy is doing a lot more than moving air, it is pumping the refrigerant. This enables the heat transfer from outside the house to inside. It will also be 100% lossy in that pretty muxh ALL of that energy will be lost as heat, also helping heat the room.
This is better than when running as an aircon. When running as a cooler all of the electrical energy is lost outside.
@Quantumcat: it doesn't necessary need to go that low, it only reversing the heat exchange cycle. With air conditioner and fridge, the cold chamber is inside your house/fridge while the heat chamber is outside. To heat the house, aircon just literally swapping the two phases around. Heat pump only manage to work with refrigerant between gas and fluid state. In the heat chamber, gas is compressed to become fluid and the fluid pass to cold chamber where it will be force to be at low pressure to vaporise.
A previous response mentioned the UK. I used them there and they are awful.
Nice and warm in the morning but you need to press the boost button in the evening using electricity at peak rates which ends up costing more.
Best way to save money is to ditch AGL. They are way over priced. I actually laughed when I read you're trying to talk to AGL about saving money.
I have seen these when I lived in England, but I have never seen them in Oz.
Not a very good method of heating, and it runs out of puff in the evening.
Reverse cycle AC is the cheapest way to heat, doubly so if you have solar panels and can use the free electricity during the day.
That said, I see you are in Adelaide, where electricity is the costliest, and the gas prices aren't as bad.