Thankfully, change is in the air. New Zealand’s Emissions Reduction Plan outlines a clear and decisive action to ban low and medium-temperature coal boilers by 2037. And that's not all – schools will be coal boiler-free by 2025. With the writing on the wall for dirty fossil fuel boilers, cleaner alternatives, like heat pumps and biomass energy sources are stepping up to the plate.
Heat pumps, especially, are a highly energy-efficient alternative to traditional coal and diesel boilers. They can deliver up to three times more energy than the electricity they use. They do this by transferring heat from the air (or ground), rather than creating heat through burning fossil fuels.
Tallying up the benefits
Compared with coal boilers, heat pumps are easier to run and maintain. Coal boilers need daily attendance and a full-time employee to keep them running, including cleaning out the ashtray. But heat pumps are self-sustained and require no daily attention. They take electricity and move energy around, with much lower carbon emissions. Although there are concerns about refrigerants used in some heat pumps, a well-installed and maintained heat pump system that doesn’t leak refrigerant and is professionally decommissioned at the end of its life poses no issue.
The cost advantage of heat pump systems is significant compared with boilers. Ministry for the Environment figures show that compared with a diesel boiler, a heat pump system can reduce heating fuel costs by 65 percent and lower CO2 emissions by over 85 percent - resulting in a payback period of about 10 years.
That said, although electric alternatives like heat pumps are a good option for low and medium temperature boilers, they’re not suitable for replacing industrial boilers that operate at ultra-high temperatures. This is due to the limitations of heat pumps, which can’t easily go beyond 70 degrees Celsius. In such cases, woody biomass boilers offer a solution that is significantly more carbon-efficient than fossil fuels.
Most sites that use coal boilers for heating distribute 100-degree Celsius water, even though this temperature isn’t needed (or optimal) for most radiators. So, in another win for the environment, less thermal energy losses in a heat pump distribution system mean even more energy savings to be gained. In situations where 100-degree water is necessary with a heat pump system, top-up heating elements can be installed to provide the hot temperature required.
Careful planning needed
Our team is in the process of replacing the coal boiler system at a large hospital site in the South Island. To start, we thoroughly examined their current infrastructure, which consists of a three-boiler system with a plant room, heat exchanger, and pumps used to distribute heated water.
Our solution for the hospital involves implementing two reversible chiller / heat pump units that can provide both low-temperature heated water and chilled water. This will create a more energy-efficient and sustainable heating and cooling system, helping the hospital reduce its carbon footprint and providing optimal comfort for patients and staff.
Transitioning from coal fired boilers to heat pumps presents a few challenges and obstacles. Power supply to the site needs to be able to handle the energy requirements of the heat pumps. Distribution systems and terminal units must also be sized to accommodate the lower water temperature produced by heat pumps.
Deciding whether to replace a coal boiler heating system with a heat pump system needs careful planning to ensure that all the bits of the system are appropriately sized to achieve maximum efficiency. Things you’ll need to consider include the temperatures you want from the system, whether you’ll use it for heating, cooling, or both.
Commercial grade heat pumps are large units that can transport heat from inside a building to outside, in which case they’re called ‘chillers’; or from outside the building to inside, in which case they’re called ‘heat pumps.’ Most units can do both depending on the season, which is a big capital cost money saver.
The next factor to consider is whether you need simultaneous heating and cooling. This is often the case in large hospitals, for example. In these cases, it’s more practical to use a multifunction heat pump that facilitates heat exchange between the heating and cooling sides, without expelling any energy to the outside air. This approach involves transferring energy from the cooling side to the heating side. It lets heating and cooling be provided simultaneously at even higher efficiency ratios.
It’s vital to avoid a one-for-one replacement of an existing coal boiler plant with the same capacity of heat pumps because the sizing of original coal plants can often be inaccurate. With a coal boiler, adding another 200 kilowatts of capacity may not have a significant impact as only the required amount of coal is burned on-site. However, specifying a heat pump unit for an additional 200 kilowatts of capacity would lead to increased costs as everything, including distribution and terminal units, would need to be scaled up. It’s crucial to harness usage data to determine the demand of your site; then size your heat pumps accordingly.
Replacing commercial coal boilers with heat pump systems is a promising solution to addressing the negative impacts of coal on the environment and human health. Yes, the initial investment can be higher, but the long-term benefits, including reduced carbon emissions, better air quality, and lower operating costs, make it a practical and sustainable choice for businesses looking towards a greener future.
.png)
