Energy-saving challenge gets technical

16 October, 2008

When Rob from Corbans Viticulture first contacted us, it was clear from his project description that a challenge lay ahead.

The project brief was to construct two coolstores, side by side, that could maintain variable set points of +2 degrees when set at a minimum temperature and 26 degrees at maximum temperature, whilst also maintaining an relative humidity of 90% at the upper set point.

This in itself is a reasonably straight forward installation if approached using traditional methods such as heat pumps, electric re-heat and a hot water heat exchanger, amongst others.

However, Corbans Viticulture vision to go ‘green’ required a coolstore system that not only functioned to specified parameters but also delivered maximum energy efficiency and savings.

The idea is actually quite simple, but the trick is the total flexibility of the design.

What was required was the use of heat energy from either of the rooms when they were cooling and then pumping this warm air into the next room, should it require heating at that time. We soon realised that to control and safety interlock all the equipment, would require a very complex system so Thermal Solutions was called on to design, prove, install and commission the entire control system.

The basic layout is to have the compressor, receiver and evaporator for each room installed as normal but the location of each condenser transportable between the rooms. When both rooms are in cooling mode, the dampers would open to discharge warm air into the atmosphere. When one room is heating and the other is cooling, the dampers open to allow warm air to be drawn out of the cooling room, through the condenser and discharged back into the room that is heating. If the first room completes its cycle ahead of the other, only then would the electric heating take over until that room cycles again.

The design

The team at Thermal Solutions designed the system so both of the refrigeration condensing coils were located in custom-built fan houses, complete with a motorised spill and recycle dampers, fans and electric boost heat coils, ducting and air distribution diffusers. Each coolstore has a conventional DX evaporator and a humidification device.

All of the above are complete with mandatory safety switches, including airflow, over temperature and over current devices as well as internal operation interlocks so that, for example, it would be impossible for a compressor to run without the condenser fan operating.

During our initial trials we were typically achieving air temperatures of 44 degrees Celsius from our condenser coils. This meant that a maximum temperature of 26 degrees could be easily  achieved - much of that for free!

During normal operation, Corbans will enjoy the benefit of approximately 18 kWs of free heat running per hour, which would otherwise have been rejected to the atmosphere. Whilst this may not sound like much, it equates to savings of approximately 150kW per day and will result in noticeable energy savings over the lifespan of the equipment.

Software and Control

In order for Corbans Viticulture to quality assure their product to their clients, Rob needed multiple air temperature sample points, linked back to a central supervisory PC based system, including alarms, historical graphs and event plotting. Thermal Solutions was to do exactly that, via  a Carrel brand product called Plant Visor.

Rob can now access, adjust and monitor the coolstores performance from any PC that has internet access. Even when he is working abroad he can change the set points or review the temperature events.

This means that accurate temperature control is always achieved - an essential component to ensure product quality for Corbans clients. We call this the Perfect Thermal Solution - happy clients, free energy, less costs.