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Energy-efficiency for the Midrand Graduate Institute

State-of-the-art European technology supplied by SEG Solar Energy (Pty) Ltd

By Kelly-Ann Prinsloo

When a new housing development at the Midrand Graduate Institute needed an energy-efficient solar water heating system, Sonnenkraft rose to the challenge. Werner Sebastian, chief executive officer of Sonnenkraft SA and SEG Solar Energy, has successfully designed and installed an 18 000ℓ solar water heating system for new student housing at the Midrand Graduate Institute’s Whitehouse complex.

Sonnenkraft specialises in the field of solar thermal as well as photovoltaic systems in the residential and commercial markets.

State-of-the-art European technology supplied by SEG Solar Energy (Pty) Ltd is used in this closed circuit installation, ensuring low maintenance and high life expectancy.

Sonnenkraft believes in supplying its customers with efficiently designed systems using only the highest quality of European technology, installation and products available.

Together with its training partners, SOLAC Solar academy and AEE Intec, Sonnenkfraft also strives towards further education and training in terms of renewable energy and system efficiency.

Characteristics of the system
The 18 000ℓ solar thermal hot water system was installed with a total of 250m² flat plate 2.5m2 Alpin Easy solar collectors. The plant room equipment includes plate heat exchanger technology, providing a total of 450ℓ per minute of instantly hot water to the student bathrooms. The plant room also includes stratified solar charging stations equipped with high efficiency brazed plate heat exchangers ensuring efficient heat transfer from the collectors into the tanks. The back-up heat source used in this installation is an 80kW heat pump system.

The system was designed as a closed circuit installation using only plate heat exchanger technology in order to transfer heat.

The heat that is produced from the solar collectors is transferred into the tanks via the plate heat exchangers in the stratified solar charging stations. Through this station, heat is stratified into different layers of the storage tanks depending on the temperature provided from the solar system. This is automatically controlled via the solar controller provided as part of the solar station.

The 12 x 1 500ℓ storage tanks are also connected as a closed circuit system. Because these tanks are not internally coated, it is not possible to use them as a flow-through hot water system. 100mm insulation is provided around these tanks and, with four connection levels from one tank to the next, stratification is possible.

Through an integrated plate heat exchanger, the fresh water modules provide instantly hot water up to 450ℓ per minute. The module also includes an integrated hot water circulation pump for the hot water reticulation line, which is split to different student housing blocks. The circulation return is also stratified back into the tanks. The fresh water module includes a state-of-the-art controller in order to set temperatures and circulation schedules.

Because the fresh water module provides instantly hot water, there is no chance for the formation of waterborne diseases such as legionella. This technology is therefore highly recommended for all industries, residential, commercial and industrial applications.

Energy-efficient WILO pumps are used in the above-mentioned modules, ensuring low running costs for the whole plant room.

The heat pump backup is directly connected to the master storage tanks (therefore indirect), assisting the solar system in keeping the water temperature to a required level if needed.

As the only open circuit of this system is the cold water supply to the fresh water module’s plate heat exchanger, the life expectancy of the system is very high with low maintenance required.

High-quality Geberit Mapress carbon steel pipework was used with stainless steel pipe cladding and rockwool insulation, ensuring no leaks and minimal heat loss in the system. This, of course, also complements the aesthetics of the system.

Roof-mounted systems, which are specifically designed and manufactured for the installation of the solar energy collectors, consist of only aluminium and stainless steel, and corrosion is therefore not possible.

In order to keep track of system efficiency and maintenance schedules, the system is equipped with data logging that provides remote real-time data in terms of pump capacities, temperatures and efficiency at any time.

This system has been operational since March 2015.


System specifications

  • Total m2 of panels: 250m2
  • Tank storage: 18 000ℓ
  • Province: Gauteng
  • Year commissioned: 2015
  • Tank construction: Black vessel
  • Litre/m2: 72
  • Back-up heating: 80kW heat pump
  • Solar heat transfer to tank: 200kW heat exchanger capacity
  • Potable hot water availability: 450ℓ/min at 950kW heat exchanger capacity
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