green energy

4 Articles

A Smarter Solar Water Heater

February 25, 2024 by 79 Comments

Installing solar power at a home is a great way to reduce electricity bills, especially as the cost of solar panels and their associated electronics continue to plummet. Not every utility allows selling solar back to the grid, though, so if you’re like [Rogan] who lives in South Africa you’ll need to come up with some clever tricks to use the solar energy each day while it’s available to keep from wasting any. He’s devised this system for his water heater that takes care of some of this excess incoming energy.

A normal water heater, at least one based on electric resistive heaters, attempts to maintain a small range of temperatures within the insulated tank. If the temperature drops due to use or loss to the environment, the heaters turn on to bring the temperature back up. This automation system does essentially the same thing, but allows a much wider range of temperatures depending on the time of day. Essentially, it allows the water heater to get much hotter during times when solar energy is available, and lets it drop to lower values before running the heater on utility electricity during times when it isn’t. Using a combination ESP32 and ATtiny to both control the heater and report its temperature, all that’s left is to program Home Assistant to get the new system to interact with the solar system’s battery charge state and available incoming solar energy.

While it’s an elegantly simple system that also affords ample hot water for morning showers, large efficiency gains like this can be low-hanging fruit to even more home energy savings than solar alone provides on paper. Effectively the water heater becomes another type of battery in [Rogan]’s home, capable of storing energy at least for the day in the form of hot water. There are a few other ways of storing excess renewable energy as well, although they might require more resources than are typically available at home.

Floating Solar Farms Are Taking The World’s Reservoirs By Storm

January 24, 2022 by 61 Comments

Photovoltaic solar panels are wonderful things, capable of capturing mere light and turning it into useful electricity. They’re often installed on residential and commercial rooftops for offsetting energy use at the source.

However, for grid-scale generation, they’re usually deployed in huge farms on tracts of land in areas that receive plenty of direct sunlight. These requirements can often put solar farms in conflict with farm-farms — the sunlight that is good for solar panels is also good for growing plants, specifically those we grow for food.

One of the more interesting ideas, however, is to create solar arrays that float on water. Unlike some of the wackier ideas out there, this one comes with some genuinely interesting engineering benefits, too!

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Making Coffee With Hydrogen

October 9, 2021 by 17 Comments

Something of a Holy Grail among engineers with an interest in a low-carbon future is the idea of replacing fossil fuel gasses with hydrogen. There are various schemes, but they all suffer from the problem that hydrogen is difficult stuff to store or transport. It’s not easily liquefied, and the tiny size of its molecule means that many containment materials that are fine for methane simply won’t hold on to it.

[Isographer] has an idea: to transport the energy not as hydrogen but as metallic aluminium, and generate hydrogen by reaction with aqueous sodium hydroxide. He’s demonstrated it by generating enough hydrogen to make a cup of coffee, as you can see in the video below the break.

It’s obviously very successful, but how does it stack up from a green perspective? The feedstocks are aluminium and sodium hydroxide, and aside from the hydrogen it produces sodium aluminate. Aluminium is produced by electrolysis of molten bauxite and uses vast amounts of energy to produce, but since it is often most economic to do so using hydroelectric power then it can be a zero-carbon store of energy. Sodium hydroxide is also produced by an electrolytic process, this time using brine as the feedstock, so it also has the potential to be produced with low-carbon electricity. Meanwhile the sodium aluminate solution is a cisutic base, but one that readily degrades to inert aluminium oxide and hydroxide in the environment. So while it can’t be guaranteed that the feedstock he’s using is low-carbon, it’s certainly a possibility.

So given scrap aluminium and an assortment of jars it’s possible to make a cup of hot coffee. It’s pretty obvious that this technology won’t be used in the home in this way, but does that make it useless? It’s not difficult to imagine energy being transported over distances as heavy-but-harmless aluminium metal, and we’re already seeing a different chemistry with the same goal being used to power vehicles.

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Fueling With Ammonia

March 3, 2021 by 68 Comments

There’s a major push now to find energy sources with smaller carbon footprints. The maritime shipping industry, according to IEEE Spectrum, is going towards ammonia. Burning ammonia produces no CO2 and it isn’t hard to make. It doesn’t require special storage techniques as hydrogen does and it has ten times the energy density of a modern lithium-ion battery.

You can burn ammonia for internal combustion or use it in a fuel cell. However, there are two problems. First, no ships are currently using the fuel and second most ammonia today is made using a very carbon-intensive process. However it is possible to create “green” ammonia, and projects in Finland, Germany, and Norway are on schedule to start using ammonia-powered ships over the next couple of years.

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