Tshwane Electrical Department; Atmospheric pressure storage system.

Holms and Friends: Atmospheric pressure storage system with 36 m2 collector & heat pump.

Short description of the atmospheric pressure storage system

A local municipality tender to ensure the newly built electrical department building complies to the National Building standard SANS 10400 XA. A very unique “Text Book” installation to demonstrate the following Solar system principles: High Pressure Indirect Glycol circulation through the flat plate panels Low pressure indirect potable water thermal storage in Polymeric storage technology Indirect high pressure on-demand supply through a “Fresh Water Station” Heat Exchanger Not the biggest installation, however integrating the technologies in such a way that the system is extremely cost competitive.

Conceptualized to attain a very long expected product life (> 20 years). CHARACTERISTICS OF THE SYSTEM What is fascinating about this system is the ingenuity and design skill that has gone into the system. It illustrates the simplicity to convince the local governments to integrate renewable energy into Government Buildings and the solution to conform to building standards and Energy Efficiency standards. The system has 36m2 flat plate collectors (thermal capacity = 25.2kWth) conceptualized at low flow with a variable speed, high efficiency, temperature controlled solar charging pump. The collectors are arranged in a combination of parallel and series configuration to avoid high resistance. The heat exchangers have long lengths with minimal resistance.

The 5 000-litre polymeric tank is reinforced with a steel mesh to ensure longevity. A 36 kWth standby heat pump delivers approximately 40 – 45% of the total energy requirement, depending on hot water requirements. The storage capacity allows for the heat pump to only run day time when the CoP is better. The fresh water station has a 60 kW exchange capacity to ensure low temperature feedback water to the storage vessel. Both primary and secondary pumps are of high efficiency class A rating and electronically speed controlled.