Solar solution for Wolwekrans

The world's largest mining group, BHP Billiton, recently invested in a solar water heating solution by Selected Energy. The Wolwekrans mine installed a solar water heating solution for its five change houses. The solar heating solution provides 5 800 litres of hot water per shift, using one heatstore with 40 flat plate collectors and two heat pumps on each of the five change houses.

According to Selected Energy's commercial consultant, Chris Elliott, the Wolwekrans solar solution was based on a number of calculations, including projected electricity consumption patterns.

"Unlike residential installations, commercial water heating solutions can be used in a number of ways to ensure constant hot water," said Elliott in an interview.

"Because commercial institutions, like mines, hotels and hostels, need large amounts of hot water throughout the day, a purely solar solution is often used with a number of other electricity saving methods to ensure minimum electricity usage. Combining various solutions guarantees hot water, even during periods of low radiation or at night."

"Each commercial installation differs, based on the amount of energy needed to heat water. To determine energy needs, we had to consider different factors. First, we had to take into account whether the installation was on a new building or on an existing building," continued Elliott.

Elliott explained that the Wolwekrans installation was a so-called greenfield installation, which means the water heating solution was installed on a new building. There was no way to monitor current usage, so the Selected Energy team had to calculate probable electricity consumption. The first step was to determine how much hot water the change houses would require for showering and laundry per shift.

"First, we had to look at the reason for showering. For example, at gold mines miners are required to take a quick shower to rinse off the gold dust, which is then collected and processed for commercial use. The amount of hot water needed for that type of shower differs vastly from the amount of water needed per shower at a coalmine. The Wolwekrans mine is a traditional coalmine, which means the miners require an average of 80 litres of hot water per shower," said Elliott.

Elliott then determined the average temperature the water had to be heated to. The next step was to determine how much hot water was required per shift.

"Wolwekrans needed hot water for showers and laundry. We multiplied the number of people per shift with the amount of water needed per shower. After that, we calculated the amount of hot water needed for washing per shift," said Elliott.

Taking into account these variables and including standing heat losses and heat lost in the ring main, the Selected Energy team calculated the kilowatt-hours (kWh) required to heat water from the ambient temperature to the required shower temperature.

"Once we understand how many kWh we have to produce to provide sufficient hot water per shift, we can start looking at possible water heating solutions," said Elliott.

Elliott encouraged commercial institutions to closely monitor electricity consumption or to carefully calculate estimated consumption before investing in a solar solution.

For more information on the Selected Energy commercial offering, contact Chris Elliott on 071-898-2921 or e-mail chrise@solahart.co.za