Last week a workshop on ‘Energy solutions in Greenhouses’ was held in Pretoria. About 30 people attended the meeting. The meeting was a great success, combining the (South) African real farm-cases and the Dutch expertise. The workshop was organised by the Agricultural Research Council and Greenport Holland International.

For much of the past three decades, electricity prices in South Africa have been low. But from 2008 the trend in prices took a dramatic turn when, in response to serious power supply shortages, Eskom embarked on a massive build programme to increase power generation capacity. Between 2008 and 2011 real electricity prices rose by 78%. It is argued that electricity prices will need to continue rise towards ‘cost-reflective’ levels so that a repeat of the costly over-investment in Generation capacity in the late 1980s and the current supply shortages can be avoided. So far, for the last two years this has resulted in again yearly (controlled) increases of about 16%.

With the increasing demand for high quality, safe and fresh food, the demand for fully optimally controlled production and postharvest/logistics has increased as well. Influencing the Greenhouse conditions for the best yield or quality, the right irrigation and cooling the product in storage is asking more and more energy.

During the workshop, Mr. Martin Helmich of Hoogendoorn Growth Management presented a project on the use of solar energy for electrical and thermal energy generation.

This project has been put into practice at Olij Roses in Naivasha (Kenya) earlier this year and aims at demonstrating a cost-effective use of solar energy that offers the possibility to run a farm independent of local energy suppliers and to produce in an environmental friendly way.

In the project solar panels are installed to produce electrical energy and solar heat collectors generate thermal energy. Part of the energy that the solar panels produce is directly used by pumps and motors in the greenhouse. The excess energy is stored in a battery-pack from which energy can be tapped during the night. 

Thermal energy is stored in a heat storage tank from which part of the farm can be heated during the night.

The project partners expect a reduction in energy costs up to 40% and - through the heating of the greenhouse- a greenhouse climate improvement and increased production and quality. Estimated payback time on the technologies for a 3-ha production area is:
  • <4 years for the total system; combining heat and power: 175 MWh per year / 50 W/m2 on 4000m2 per year
  • 2.5 years for the solar collector system; heating only 
  • 4 years for the PV panel system; power only
  • 6 years for the PV panel system with the batteries
Because of the enthusiasm for the project, the participants are invited to visit the project in January.

Also other cases were brought in by growers like Berg en Dal Nursery, Klein Karoo, Patio Plant and UniSA Horticultural Centre.

The workshop was highly appreciated and a follow-up will be organised in March 2015. 

For more information: 
Agricultural Research Council
Petrus Britz 

Greenport Holland 
Lisette Bakker