There is a vast array of technologies – both emerging and established – that can exploit readily available natural energy sources to provide power generation, space heating and water heating. One concept gaining popularity is combining disparate sustainable energy solutions together to multiply energy savings.
Bringing together solar photovoltaic (PV) power generation systems with heat pump technology can provide real opportunities for increased energy savings. Heat pumps typically harness ambient heat energy from the air or ground, using this energy for potable water heating or space heating. This is achieved through a vapour-compression refrigeration device, comprising a condenser, expansion valve, evaporator and compressor. However, while heat pumps essentially harness heat energy for free, a small amount of power is still required to operate the compressor. Combining a heat pump with solar PV electricity generation can therefore result in a water-heating solution with no net conventional energy requirements.
Zero net carbon impact
Solar PV systems are most commonly installed in conjunction with grid-supply architecture, whereby a modified meter allows generated electricity to be sold back to the grid. In effect, a grid-connected set up uses the grid to ‘store’ unused electricity generated during the day and provides a power supply when the solar PV panels are unable to meet demand.
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Heat pumps function most efficiently when allowed to operate for several hours during the day to bring a volume of stored water to an optimal temperature for use later in the day. In this respect, solar PV generation can supply power to the heat pump’s compressor exactly when it is required.
The advantages of a hybrid solar PV/heat pump solution are many – not least the achievement of a zero net carbon impact. The financial implications of a system using only renewable energy are obvious. However, there are also less direct – but very significant – benefits on offer, such as reducing the burden on the network demand. Electricity demand is still growing in all areas of Australia, meaning that any move that lightens the load on power generation companies will aid demand-side management and potentially help mitigate the need for new fossil-fuelled power stations in the future.
While renewable energy systems tend to incur a higher initial investment cost, they are heavily subsidised through various federal and state rebate schemes. Feed-in tariffs (FiT) – the rates at which generated electricity can be sold back to the grid – provide an incentive to maximise the quantity of electricity generated. Together, rebates and FiTs can dramatically reduce the payback period of renewable energy systems to as little as four to seven years.
Resource efficiency
Currently, FiTs in most states are set at about 250 per cent of the cost per kilowatt hour of energy bought from the grid. Under a net FiT scheme, a household is able to sell unused generated electricity back to the grid for a substantially higher price than it costs them to buy electricity from their supplier. This means that under such a scheme it pays – literally – to minimise electricity usage during the day and ‘load-shift’ power-hungry activities to the evening or early morning.
Additionally, households that have invested in renewable energy systems typically display increased energy consciousness, helping alleviate power wastage. Case studies have shown that this increased resource consciousness also often translates into other environmental savings, such as water efficiency and waste minimisation.
To get the best out of a solar PV/heat pump combination, it is paramount to understand the technology and its capabilities. Just as drivers of hybrid petrol/electric cars shift their focus from acceleration to fuel efficiency – and adjust their driving style accordingly – users of sustainable heating systems need to work with the technology to achieve the best results. In this way, the longevity of the system can be assured, achieving the desired heating results while attaining ongoing and significant energy savings long into the future.
The Stiebel Eltron group is a global designer and manufacturer of innovative water heating, ventilation, air-conditioning and refrigeration systems technology, headquartered in Holzminden, Germany. Its broad spectrum of solutions includes instantaneous electric water heaters, heat pumps, space heaters and water filtration systems – all designed to combine safety, convenience and low energy consumption.
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