What is a Heat Pump?
A heat pump is a device that can transfer (pump) heat in the opposite direction to its normal direction of flow. Rather than ‘producing’ hear (like any other heating method) it moves it. In fact, your fridge is a heat pump and it ‘pumps’ heat out of your food and then ejects the heat to the room via the warm grille at the back. But in the context of this website, the technology described is used to replace a conventional home heating system.
The heat delivered is not free because you do need some energy input to operation the system, but intriguingly heat pumps can produce far more useful heat energy than the energy input needed to drive them. Indeed, this is usually the motivation for installing one. Moreover, the net CO2 emissions in a correctly configured installation are usually lower than those of conventional fuels, like oil or gas, which they might displace. For this reason they are classed as a ‘low carbon’ technology and a recognized form of heating worldwide.
Why Heat Pumps?
Heating is expensive, both in money and environmental terms. Heat pumps can potentially reduce the amount of energy input required, so can reduce both cash and environmental costs. That’s it, in a nutshell.
Until relatively recently these ‘costs’ have not been considered a matter for concern: fuel has been cheap and the phrase ‘environmentally impact’ didn’t even exist. With the twin problems of climate change and peak oil now looming, any approach that can reduce consumption of fossil fuels deserves attention, and heat pumps are definitely one of them.
Our options are either to generate energy from the natural forces of the waves, wind or rivers, collecting energy from the sun, or by reducing our needs through insulation and minimizing waste. Clearly a mix of strategies is needed.
Heat pumps are sometimes categorized alongside renewables like wind, wave, solar and hydro, but heat pumps are only partly renewable since, at the present time, the energy input that is required is rarely from a renewable source. On the other hand, unlike most other renewables, they can operate on-demand at any time.
The Future of Heat Pumps
Over the years, heat pumps have undergone small developmental improvements, as have many technologies, from the bike to the boiler. The laws of physics cast limits on what is attainable, as evidenced by the internal combustion engine that has only improved modestly over the last 100 years (unlike electronics that improve in quantum leaps). It is unlikely that we will see any dramatic breakthrough with heat-pump design, just modest step-by-step improvements.
Where things will improve, however, is when manufacturers produce heat pumps in ever-greater numbers and manufacturing techniques evolve, so that things become more cost-effective. The area that currently requires the most attention, however, is that of the end-use of the equipment. From planning to installing, this is where we still have a lot to learn, as we hopefully realise what works well and what doesn’t.
Another important prerequisite for sustainable heat-pump installations is a trained and capable workforce, familiar with installing the technology in a range of installations. In other countries where the heat-pump installation industry has more experience, they have already learned from past errors. In New Zealand, the building industry is in a period of transition, whilst it embraces demands to reduce energy. The heating industry is still learning how to adapt to the many changes it encounters and as such there are occasionally poor installations that perform badly, attract negative publicity and give the industry as a whole a bad name. In countries where there is a much great market penetration of heat-pump technology, few installations fail to provide both financial and environmental benefits.
With present awareness of the need to conserve energy resources, it seems that heat pumps will have many roles to play in the future. There is no doubt that the heat pump is here to stay.
Heat Pump Efficiency
Heat pumps have been around for many years. This rather mystical device promises to deliver 3kW of heat for every kW of electricity consumed. This figure seems to creep up from 3 to 4around the first years of the twenty-first century. However, the recent field studies carried out by the EECA indicate that most of NZ’s installations are falling well short of expectations.
Some think that even the original forecast of 3 could be optimistic, but there is no doubt whatsoever that there are many systems running with figures of 4.
Planning a Heat Pumps Installation – Things to Consider
Prior to deciding if a heat pump is right for you or not, one should be aware that there are many ways of reducing your energy expenditure. Most of these will involve capital outlay and the principle of ‘opportunity cost’ may be important here, since there is rarely an unlimited budget. If you spend on one option, you cannot afford another, so a choice between different options must be made. For example, you could choose between high-specification external thermal insulation and a new boiler, or a heat pump and cheaper insulation (assuming each option costs the same). The choices must be weighed up with respect to predicted savings in the long and short-term.
Since there are many routes that could be taken, it is useful to consider things in this order:
- Minimzing your energy demand
- Producing heat more economically and environmentally.
- Reducing energy demand is always the best starting point. There are any factors that may affect your energy needs, such as the number of occupants in the house, their ages, how warm it needs to be, whether it is occupied all day and so on. Your overall strategy should start with trying to minimize the overall strategy should start with trying to minimize the overall energy requirement. All the basic rules of energy conservation should be observed and there is plenty of advice about this available. Insulation is nearly always the prime option, even if it is very expensive. It should last indefinitely and should not require any attention. But there is sometimes a limit to levels of insulation that can be achieved, e.g. losing wall space due to internal insulation might be unwelcome and external insulation might be impractical.
Once your heat needs have been assessed, the method of heating (potentially a heat pump) can then be considered. Some people install a heat pump for environmental reasons and as an investment for the future, others are more concerned with their immediate running costs, so different people will have different concerns. Generally though, everyone will want to highest energy efficiency for the least installation upheaval and cost.
The following list suggests some initial questions to consider:
- Will a heat pump be suitable for my house and lifestyle?
- What different heat pump options do I have?
- What will a system cost to install?
- What are likely long-term running costs?
- How disruptive will the installation be?
- What CO2 savings will I achieve?
- What else could I do instead?
