February 2011


Global Warming25 Feb 2011 01:27 pm

Chris Yelland and the team at EE Publishers are the gurus of all things to do with electric power. So all South Africans would do well to pay attention to their analysis in this morning’s EE News: Brace yourself – the electricity price trajectory for years to come…
The article makes the point that when the National Energy Regulator of South Africa nixed Eskom’s proposed annual rate increases of up to 35 percent . . .

Many consumers breathed a sigh of relief, but a fact that received little attention at the time was the indication by NERSA that the 25% p.a. increases allowed for 2010, 2011 and 2012 would now likely continue after 2012.

The article later adds:

Irrespective of which scenario is considered, the projected electricity prices in the draft IRP 2010 show annual increases well above inflation up to 2021, and it would appear that the golden era of Eskom price increases at or below inflation will only arrive thereafter.

And concludes:

. . . take heart! Electricity prices should level off in about ten years time. Highlight 2021 in your diary as the dawn of a new era of Eskom price increases in line with inflation. Maybe…

I ran some of these numbers through a spreadsheet to see what they might mean to my electricity bill. For Eskom to reach the prices it originally envisioned before NERSA put a lid on annual increases, 25 percent price hikes will have to continue to at least 2014. Assuming that City Power of Johannesburg passes these increases on to residential users, this means that the 68 cents per kilowatt hour we pay today could leap to R1.66 in the next 3 years.

I don’t raise this issue to increase anyone’s blood pressure. What interests me is that this information completely changes any cost-benefit analysis of investments in energy efficiency at home. Back at my spreadsheets I find that  a solar hot water system that would pay for itself in 5 years at 68 cents a kilowatt hours, recoups the outlay in just 2 years at R1.66 a kilowatt hour. An efficient, variable-speed pool pump that makes sense as an investment over 7 years, suddenly makes much more sense by turning profitable in just 3 years.  LED lights that were expected to cover their costs in 6 years achieve that mark in 2 1/2 years.

I don’t think that every effort to make a greener house has to pay for itself. A little bit of financial analysis does help point out the changes that can make the greatest impact for the least expense, however. Eskom may not be doing our budgets any favours, but it sure is turning the cost-benefit analysis for eco-friendly investments green.

Appliances &Solar11 Feb 2011 01:15 pm

Dishwasher Plus Solar PanelsEqual SignGreen Smiley

When I first wrote on GreenerHouse about dishwashers, I lamented that I could not find one with a hot-water inlet. For most of the year, I have an excess of solar-heated hot water sitting in tanks, so it is a waste for my dishwasher to be electrically heating cold water. At the time, I had been misinformed by a Bosch technical expert that the inlet to my dishwasher could handle a maximum of 40 degrees. Like an idiot, I hadn’t read the manual, which says that the inlet can take up to 60-degree water.

Water heated by flat-panel solar collectors does not tend to rise much above 60 degrees, and my kitchen is far—too far—from my water tanks to ever get to 60 degrees at the tap, according to my thermometer. (Vacuum-tube panels do often produce much hotter water, and may require a thermostatic mixer to keep temperatures at safe levels.)

So I recently asked my plumber to connect the hot water to my dishwasher. My hypothesis was that the thermostat inside the dishwasher would switch off the heating element more quickly with warm water entering the machine. Using a cold-water feed, this Bosch, A-rated model uses approximately 1 kWh per load at the 35 degree “Quick Wash” setting. After connecting the hot water, I recalculated the energy consumption, using the technique outlined here. It has fallen to 0.7 kWh per wash. Over the course of a year, this simple change should save about 100 kWh preventing some 100 kilograms of carbon dioxide from being released into the atmosphere.

If my dishwasher were located closer to the hot water, the savings would be far greater. In designing a new house, ideally the north-facing roof, solar panels, hot-water tanks, bathrooms and kitchen should all be as close as possible. If this is not possible, small-diameter Pex pipes can help overcome heat loss over long distances. (Combining Pex pipes and vacuum-tube solar collectors is asking for a meltdown, however.)

I compensate by running the hot water in the sink, usually while washing pots and pans, immediately before switching on the dishwasher. That way the water enters the machine hot for the wash cycle, though only slightly warm after the copper pipes have cooled the water for the two rinse cycles. One day I will try insulating the pipes and see if I get even better results. In the winter, when the sun does not always provide enough hot water, I will try to run the dishwasher in the late morning, so as not to deplete the evening supply of hot water.

Coincidentally, just days after my plumber had made the connection and before I had a chance to measure my results or write about it, a GreenerHouse reader published a comment here, reporting how pleased he was with his hot-water connection to his dishwasher. All green minds think alike.