Wind, solar and diesel: Let the numbers tell you the story

Wind, solar and diesel: Let the numbers tell you the story

Prof. Paul Wessels, owner of Southwest Windpower’s Whisper 200 (1 KW) and Whisper 500 (3.2 KW) wind turbines, provided the Company his complete system metrics. The two turbines are components of a larger hybrid system that is completed with solar and diesel. The energy produced by the system powers Wessels’ rural off-grid cattle farm. The data is broken down by each component of his system, as described in our case study from a previous blog post.  Prof. Wessels, who keeps meticulous data records, monitors his off-grid system year round; however, the table consists of specifics from each season in South Africa, which is comprised of mid-summer, mid-spring and mid-winter through the months of January, April, July and October 2010 respectively.

Component Annual Energy Ah Annual Energy kWh Diesel offset: Liters Diesel offset: Gallons Savings USD CO2 offset: kg CO2 offset: lbs
Whisper 200 29,604 1066 507 134 $741 1167 2599
Whisper 500 39,396 1418 675 178 $986 1553 3459
Solar PV 177,204 6379 3038 802 $4,435 6987 15,558
Diesel 14,100 508 - - - - -
TOTAL 260,304 9,371 4,221 1,114 $6,162 9,707 21,616


Generally speaking, there is more sun per year in South Africa than there is wind. The ratio of sun to wind in Bloemfontein, central South Africa, varies substantially due to its central location.

South Africa has a Mediterranean climate that consists of mild temperatures with dry and warm summers. January is typically the hottest month of the year, subsequently making July the coldest. Sunlight consumes some 68 percent of the day.  The approximate 32 percent that remain is likely to be cloudy, shady or low sun intensity. Most wind is received along the coastal regions, exceeding some 3,760 kWh. The estimated annual wind speed for the country when measured at 10m (32 ft) high is 6 m/s (13.4 mph). The Western Cape, Northern Cape, Eastern Cape and KwaZulu-Natal receive the most amount of wind. The further inland, the less wind. Prof. Wessels’ cattle farm is situated in the central part of the country, where much lower wind speeds are typical.
To estimate how much diesel use was prevented using wind turbines and solar panels, we assumed the average cost of diesel in South Africa at approximately $1.46 USD per liter (as it was at the time of this writing). His complete renewable system offsets the emissions of about 9.707 kg or 21,616 lbs of carbon per year! He saves an approximate $6,100 USD a year. This does not take into consideration the cost of maintaining the diesel generator or the transport of the fuel to his remote location.


This one example of many where the numbers tell the story and prove that a hybrid-system, one of which consists of a combination of multiple energy sources, is extremely beneficial not only for the environment, but also to your energy budget. Take a look for yourself and let the figures persuade you to begin improving or installing your renewable energy system today!


Whisper turbines from Southwest Windpower offer clean, renewable energy that’s a viable alternative to diesel power for varied off-grid applications such as telecommunications, remote households, agriculture, water pumping, humanitarian projects, education and more. Southwest Windpower’s Whisper 100, Whisper 200 and Whisper 500 offer varying levels of output for most low-use remote power needs, and adding multiple units can scale systems up. Whisper turbines also work well with solar panels, offsetting seasonal variations in solar energy and adding night and cloudy weather generating capacity to any location with significant wind, at least 10 mph (4.4 m/s).




Share this page: