No, You Cannot ‘Power Your Home’ by One Hour of Cycling Daily

In the past days different versions of an article had popped up in my social media streams again and again – claiming that you could power your home for 24 hours by cycling for one hour.

Regular readers know that I craft my statements carefully in articles about energy, nearly as in the old times when submitting a scientific paper to a journal, with lots of phrases like Tentatively, we assume…

But in this case, I cannot say it more politely or less distinctly:

No, you cannot power your home by one hour of cycling unless the only electrical appliance in your home is the equivalent of one energy-efficient small computer. I am excluding heating and cooling anyway.

Yes, I know the original article targeted people without access to the power grid. But this information seems to have been lost in uncritical reshares with catchy headlines. Having seen lots of people – whose ‘Western’ homes will never be powered by a treadmill – discussing and cheering this idea, I want to contribute some numbers [*].

This is all the not-exactly-rocket-science math you need, so authors not adding conclusive numbers to their claims have no excuses:

Energy in kWh = Power in Watts times hours divided by 1000

Then you need to be capable to read off your yearly kWh from your utility bill, divide by 365, and/or spot the power in Watts indicated on appliances or to be googled easily.

A professional athlete can cycle at several 100 Watts for some minutes (only) and he just beats a toaster (which needs a power of 500-1000W).

So an average person cannot cycle at more than 100-200W for one hour, delivering 0,2kWh during that hour at best.

With that energy you can power a 20W notebook or light bulb for 10 hours, and nothing more.

Anything with rotating parts like water well pumps, washing machines, or appliances for cutting or mixing need much more power than that, usually a few 100W. Cycling for one hour can drive one device like that for less than half an hour.

An electric stove or a water heater needs about 2kW peak power, at half of the maximum such appliances would consume 1kWh in one hour. An energy-efficient small fridge needs 0,5kWh per day, a large one up to 4kWh.

A TV set could need 150W[**], so you might just be able to power it while watching. I don’t say that this is a bad idea – but it is just very different from ‘powering your home’.

I’ll not link those click-bait articles but an excellent website instead (for the US): Here you can estimate your daily consumption, by picking all your appliances from a list, and learn about the power each one needs. At least it should give you some feeling for the numbers, to be compared with the utility bill, and to identify the most important suckers for energy.

http://energy.gov/energysaver/estimating-appliance-and-home-electronic-energy-use

I have scrutinized our base load consumption in this article: In summer (without space heating) our house needs about 10kWh of electrical energy per day, including 1-2 kWh for heating of hot water by the heat pump. The base load – what the house needs when we are away – is about 4kWh per day.

There are numerous articles with energy statistics for different countries, I pick one at random, stating – in line with many others – that a German household needs about 10kWh per day and one in the US about 30kWh. But even for Nigeria the average value per home is about 1,5kWh, several times the output of one hour of cycling.

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[*] I’ve added this paragraph on Feb. 8 for clarification as the point came up in some discussions on my post.

[**] Depends on size, see for example this list for TVs common in Germany. I was rather thinking of a bigger one, in line with the typical values given also by the US Department of Energy (300W for a plasma TV!).

Greatest Innovation Ever

I like silly Top Something Lists. In a more serious state of mind I wondered what a list of the top inventions or top innovations of humankind might comprise.

Random googling yields list items such as The Internet, Money, Plumbing, and The Power of Story.

This list contains what my biased mind was searching for: Electricity, Water Power, The Light Bulb, The Steam Engine, The Electromagnet, The ElectronSemiconductors, The Transistor, and of course again The Internet. I argue the greatest innovation uses all these and is as important as Plumbing – actually our toilets and water supply would not work without it today: I nominate …

The Power Grid

(If this were TV, you would now see this.)

You might say that I am cheating because the power grid is not a singular invention but rather a conglomerate of diverse inventions, held together by the glue of standardization, politics, and committees. I picked the grid for that very reason.

The more I learned about the power grid the more I wondered that it works at all – at that amazing level of availability. In Austria the average downtime per customer is about 45 minutes per year, that is electric power is available 99,99% of the time. Experts state that this even has a negative impact of our ability to cope with sudden blackouts. This is called the paradox of vulnerability: the less vulnerable you are as per statistics, the less you care about very improbably but disastrous events.

At every moment the consumption of electrical energy needs to be balanced with the demand. This sounds trivial but it means that if you turn on your oven, somewhere in your country (actually: in your control area) a gas turbine needs to spin a bit faster. In Austria the gates at a pumped-storage hydropower plant will open a bit more.

If you turn on your computer or other electronic device the compensation needs to be more sophisticated as modern devices distort the nice sine function that alternate current used to be in the old times.

Kölnbreinsperre from Arlhöhe

Storage lake, Malta power plants in Carinthia, southern Austria. Maximum power is 1,3 GW which is more than 10% of Austria’s peak power. (Wikimedia)

If consumption rises faster than demand the frequency of AC power decreases. All generators rotate in sync – most of continental Europe is one large synchronous area. The energy ‘stored’ in rotation is proportional to the square of the frequency. If the energy is not consumed the rotating masses can’t get rid of it. Since the factor of proportionality is the moment of inertia you can compensate for changes in demand by tweaking the generator, e.g. by controlling the flow of water. The grid codes agreed upon by all countries in a control area state that the operators of generators need to respond within seconds.

If something goes badly wrong the synchronous area would split into regions where generators spin with different frequencies – preventing to flow energy between these areas. This had happened in a blackout in 2006 in Europe, which was triggered by a – planned – disconnect of power lines in Germany: allowing for a ship to pass.

UCTE area split at 4 11 2006

Europe’s synchronous area split into three regions in November 2006 (Wikimedia)

What amazes me even more is that the system does still work so well, even after introducing feedback loops governed by a ‘capitalist’ market. I consider the power grid a combination of at least three networks: the network of electrical power, the communications network (stuff for cybersecurity nightmares), and a market of suppliers and customers. We can expect many new types of participants in this market as the producing consumer – the prosumer – and intermediaries aggregating demand and supply.

I am sometimes worried about the consequences of adding more smartness, intelligence and automation for technical and, above all, for commercial reasons. I am not that concerned about hackers changing the frequency of generators, but about perfectly well-controlled computers running mad at the electricity stock exchange (or by some harmless test command wreaking havoc – as described at the bottom of this post.).

In February 2012 is was really cold in middle Europe for about two weeks, and basically all power plants were up and running – not much reserve left for controlling frequency and power. There had been rumors on speculations impacting the stability of the power grid in Germany: Since the stock exchange prices of electricity were high, the balancing group representatives were said to have tweaked their forecasts. As a result the power needed was not standard power to be purchased on a market designed for that but precious energy that should have been dedicated to providing stability. The German regulator explained later that these alleged speculations had not made sense in hindsight but it cannot be ruled out that representatives were tempted to do that beforehand.

The blackout in California in 2003 is often quoted as a textbook example of a software bug affecting infrastructure, as well as the market manipulations causing the Californian ‘electricity crisis’ have been considered an unintended side-effect of market liberalization.

This is all very interesting for the engineering, physics, and IT geek (even including the geek who indulges in applying physics-style differential equations to economics). But the consumer of electrical power in me simply concludes that at all odds you should try to make yourself as self-sufficient as possible.

Advertisement for Windmill Electric Power Generating system 1897

Advertisement for Windmill Electric Power Generating system 1897. “Harper’s New Monthly Magazine” New York (Wikimedia)

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For German readers – and actually in order to keep track of that myself – I add some sources only available in German:

Statistics of disruptions by the Austrian regulator, incl. exact definitions for calculating the minutes of disruption quoted in the post.

Malta hydropower plants in Wikipedia.

Stability of the German power grid in February 2012:
Austrian newspaper article – translating to ‘Gambling until Blackout’, a bit sensationalist.
Evaluation by the German regulator, see page 61. They really use the term temptation.