South Africa is running short of electricity. Individuals and small and large businesses can contribute by saving as much energy as possible, particularly at peak times. Individuals and businesses can do more. They can generate electricity from renewable energy (RE) sources, both for own use and for exporting to the grid. Every unit of electricity generated by a grid-connected premises, no matter where it is used, saves one unit of centrally generated grid electricity.

Now , an on-grid house can go to various stages of off-grid functioning , at increasing cost as you go further and further off grid , or , rather , off fossil energy . With the rapidly increasing cost of electricity and decreasing cost of Photovoltaic (PV) systems it is becoming viable to invest in PV power when considered over the 25 year nominal life of a system. Systems are modular, so you can start small and build further as time and funds permit. The author embarked on a project that would hopefully enable him to generate sufficient PV power to satisfy the needs of an ordinary two person home in Cape Town. The first stage was to reduce electricity consumption and this was remarkably successfully achieved (70 % reduction) by simple measures. The next step was to design the PV system and install it. Thereafter management strategies had to be designed as to how best to use electrical energy from PV, from battery storage and from the grid to fulfil the needs of the house. You can build this strategy around any financial incentive schemes that may be available to optimize savings (eg Germany today). The author's 2008 future-oriented philosophy ran as follows: Use as little total energy as possible. Generate as much RE as you can at home, run your home as completely as possible from own generation with batteries, and export all your surplus . Remain connected to both grid and house-load at all times. Pull in energy from the grid automatically only if really needed by house and/or battery, off-peak if possible. Get maximally rewarded for all PV energy generated, get minimally rewarded for all energy exported, pro rata at Time-of-Use rates. Automate as many of above functions as possible.

Well, that is not the most economic (short term!) approach but it does the best for assisting the grid operators. As yet there is no equipment that can do all of that, and there are no incentives in South Africa, or even official grid connections permitted yet. There has to be quite a lot of manual input at present to achieve this. But equipment is being designed today (2012) in Germany to do exactly this (Home energy management). A local inverter can already do much of this management function.

The presentation will illustrate from personal experience the above principles , with some unexpected ups and downs and lots of learning , resulting in 93% reduction in grid electricity consumption (so far).

Presented by Dr G Anthony Keen Private

Dr Anthony Keen enjoyed an academic professional career with medical microbes (mostly viruses) for 35 years at the University of Cape Town Medical School. After retiring in 2000, he has pursued to greater depths his interest in sustainable energy and water matters.