Lifestyle Garden Centre: nursery, office & lifestyle shops, Randparkridge. Holms and Friends: 30,000-litre storage system with 480m² flat plate collector

SHORT DESCRIPTION OF THE STORAGE SYSTEM WITH FLAT PLATE COLLECTOR

The Lifestyle Garden Centre was extended in 2006-7 and required three times the amount of electricity than used before. At the time, no electricity was available nor was the infrastructure large enough to support the energy demand.

Through passive design, smart equipment choice, a building management system (BSM), night time ice storage and a large scale solar water heating (SWH) system, the total demand could be reduced by more than 60% and energy consumption was halved.

The solar water heating system supplies mainly a under floor heating system for the office, shops and nursery for sensitive plants during winter time. In addition, it provides hot water to the change rooms. A few smaller systems are also scattered over the site were the distance to the central system is too far.

GPS coordinates: -26° 5′ 42.26″, +27° 56′ 34.58″

CHARACTERISTIC’S OF THE STORAGE SYSTEM WITH FLAT PLATE COLLECTOR

The system was design to avoid high winter electricity peaks and to reduce the energy consumption. As such it uses the floor a thermal capacitor, but has a large storage vessel to bridge the late afternoon and early morning peak demand periods as a minimum. The buffer storage vessel has a capacity of 30,000-litre and due to space constraints in the existing building was place horizontal.

The under floor heating system of more than 1 200m², is divided in different zones. The zones can be individually controlled to achieve the optimum temperature. Temperatures of between 40 – 50 degrees C can be pumped into the floor and return temperatures are typically at 25⁰C.

The system is probable the largest drain down system in Africa. This means the system has no freeze protection glycol in the solar loop, but drains all water after sundown into the main hot water storage vessel. The means there is no water in the collector and/or solar loop, which means no freeze damage can occur. This strategy has major advantages in terms of maintenance and running cost, but requires special design and initial installation skills.

The collector of 480m² is connected in serial and parallel. The collector is fixed directly onto the roof at a tilt angle of 20 degrees, facing true north. This system is designed as a high flow collector system with flows of up to 40kg/m² collector. This has the advantage that the collector works at optimum efficiency, but has the disadvantage that pipe sizes are up to 108mm and a circulation pump of 5kW. The pump is controlled by a simple temperature differential controller.

As the system is a drain down, there are no heat exchangers on the solar side. Small heat exchangers transfer heat to the under floor heating and fresh water circulation loop.

CLIENT INFORMATION AND AGREEMENT TO FILM THE SYSTEM

Henning Holm has approval from client to film.

OTHER INFORMATION

• This was one of the very first large scale systems (and as such a South African record for a long time) used in the built environment.
• The system has been running since January 2007 and with an energy saving of at least 240 000kWh/annum, has saved the Lifestyle Garden Centre already a minimum of 1 920 000kWh.
• The system cost was R 1 320 968 in 2007, which is R 2 752/m² collector area. Due to the high energy demand & consumption savings, the system reached payback already in the third year.