| but if inverters were small and cheap, I would personally prefer having an exercise bike plugged into the grid. That way my exercise energy would at least be useful to someone, somewhere. You'd likely never produce enough energy to offset the energy used to create the inverter. Just to come up with a rough estimate, if the bicycle grid-tie inverter cost $200, and 25% of that cost is due to energy @ $0.10/Kwh, that's 500KwH of energy wrapped up in that inverter. If you produce an average of 100W while biking, that's 5000 hours of biking, or about 10 years of biking 10 hours a week. It might be more practical if you could harness all of the bikes in a busy gym where you could get hundreds of bike-hours of energy a day. (Ok, I made some pretty big assumptions here. First, I don't know how much energy goes into making a product or how much it costs, and it's not all electricity, there's diesel and natrual gas in mining and processing raw materials, etc). (Edit: my guess is probably not too far off, a typical phone in 2008 had around 180MJ/50Kwh of embodied energy [1], so 10X that amount for a 10 or 20 pound grid-tie inverter might be in the right ballpark. Aluminum alone has around 200MJ/kg embodied energy so a 2 pound heat sink would account for around 50KWh of the embodied energy of the device) [1] https://www.lowtechmagazine.com/2008/02/the-right-to-35.html |
Additionally, these analyses rarely take into account positive second order effects. For example if someone puts solar panels on a northern facing roof in Canada, they are unlikely to ever realize a breakeven point, and the project might not offset the embodied energy of the system (and associated emissions). But that purchase means more revenues and jobs for the solar industry. And in turn that means more investment and more economies of scale.
Basically, if we want to transition to a carbon neutral world, it is going to require a lot of people investing/purchasing projects/goods that do not make sense economically and might not initially be carbon neutral after accounting for embodied energy. Without early supporters we can only rely on government subsidies (which we already do, but obviously not enough). I personally don't think the free market can solve climate change, but if it is going to have a chance, we are going to need a lot of people to make these types of purchases/investments.
Also, another thing to consider is that the inverters lifetime is going to be directly correlated to the operating hours. So if the OP wants to hook up his exercise bike to the grid (assuming it is legal in their area), and then down the road decides to get some solar panels, that inverter will work perfectly fine for that purpose and have minimal degradation.