Enlarge / The Kariba Dam in Zimbabwe. (credit: Robert Holmes )

One of the big challenges we face regarding climate change is that we have to lower our emissions at a time when energy consumption is likely to grow. Many countries in the Global South will seek some combination of expanding access to the electric grid, increasing grid reliability, and expanding grid capacity to meet rising demand. It's estimated that demand in Africa will increase by roughly five percent a year for some time. Handling that increase while reducing emissions will be a challenge.

As things currently stand, African nations are primarily served by a mix of large hydroelectric plants—a number of smaller nations already have nearly emissions-free grids—and fossil fuels. Most plans for limiting carbon emissions going forward have involved expanding hydropower, and there are plans for adding about 100 GigaWatts of new capacity in the coming decades. But the rapid drop in the cost of wind and solar power raises questions as to whether those plans still make sense.

In many cases, the answer is no, according to a new study. Instead, it suggests that only about half of the hydropower projects make economic sense and that many African countries are better off moving ahead with other renewables. By 2050, it's estimated that half of Africa's electricity could come from wind and solar.

Enlarge / Airbus will be testing hydrogen power on a commercial airliner modified to carry an additional engine. (credit: Airbus )

A complete hydrogen fuel cell powertrain assembly occupied the pride of place in the pavilion of Beyond Aero at the recently concluded Paris Air Show. That a fuel cell system was the Toulouse-based startup’s centerpiece at the biennial aero event is an indication of the steps being taken by a range of companies, from startups to multinational corporations, toward realizing the goal of using hydrogen as fuel in the aviation sector.

“This 85 kilowatt subscale demonstrator was successfully tested a few months ago. Even though in its current form, it serves only ultralight aviation, the successful test of the powertrain is a crucial step in our technical development path for designing and building a business aircraft,” Beyond Aero co-founder Hugo Tarlé told Ars Technica.

Tarlé said that the business aircraft would have a range of 800 nautical miles and will be powered by a 1 MW powertrain. “For generating this power, there won’t be one big megawatt fuel cell. Instead, it will be multiple fuel cells. It will be based on the same technical choices that we made on the subscale demonstrator—i.e. gaseous hydrogen, fuel cell, hybridization of batteries and electric motors."

Enlarge (credit: Yuga Kurita )

One of the more threatening aspects of climate change is its potential to unleash feedbacks, or situations where warming induces changes that drive even more warming. Most of those are natural, such as a warmer ocean being able to hold less carbon dioxide, resulting in even more of the greenhouse gas in the atmosphere. But at least one potential feedback has a very human element: air conditioning.

A lot of the carbon dioxide we emit comes from the production of electricity. The heat those emissions generate causes people to run air conditioning more often, which drives more electricity use, which drives further emissions. It's a feedback that will remain a threat until we manage to green the electrical grid.

A new report released this week takes a look at that feedback from the perspective of our climate goals, examining how much more often air conditioning is likely to be used in a world at our backup goal of 2° C of warming, and comparing it to one where we actually reach our primary goal of limiting warming to 1.5°C. The answer is that it makes a big difference, but the impacts aren't evenly spread between countries.

Enlarge (credit: audioundwerbung )

In most industrialized countries, solar panels account for only a quarter to a third of the overall cost of building a solar farm. All the other expenses—additional hardware, financing, installation, permitting, etc—make up the bulk of the cost. To make the most of all these other costs, it makes sense to pay a bit more to install efficient panels that convert more of the incoming light into electricity.

Unfortunately, the cutting edge of silicon panels is already at about 25 percent efficiency, and there's no way to push the material past 29 percent. And there's an immense jump in price between those and the sorts of specialized, hyper-efficient photovoltaic hardware we use in space.

Those pricey panels have three layers of photovoltaic materials, each tuned to a different wavelength of light. So to hit something in between on the cost/efficiency scale, it makes sense to develop a two-layer device. This week saw some progress in that regard, with two separate reports of two-layer perovskite/silicon solar cells with efficiencies of well above 30 percent. Right now, they don't last long enough to be useful, but they may point the way toward developing better materials.

Enlarge / Natural gas plants like these may find themselves burning hydrogen over the next 20 years. (credit: Ron and Patty Thomas )

Today, the Biden administration formally announced its planned rules for limiting carbon emissions from the electrical grid. The rules will largely take effect in the 2030s and apply to gas- and coal-fired generating plants. Should the new plan go into effect, the operators of those plants will either need to capture carbon or replace a large fraction of their fuel with hydrogen. The rules will likely hasten coal's disappearance from the US grid and start pushing natural gas turbines to a supplemental source of power.

Whether they go into effect will largely depend on legal maneuvering and the results of future elections. But first, the rules themselves.

Clearing the air

Back in 2007, the US Supreme Court ruled that the Clean Air Act applied to greenhouse gas emissions . This allows the EPA to set state-level standards to limit the release of greenhouse gasses, with the states given some leeway on how they reach those standards. Since then, the court has clarified that these standards must be met on a per-plant basis rather than at the grid level; the EPA can't set rules that assume that the grid has more generation from solar and less from coal plants.

Enlarge (credit: John Timmer)

For many years, talking about fat-tire bikes meant you were referring to mountain bikes. But a more recent generation of bikes has dared to ask, "You call that fat?" These bikes, equipped with comically wide tires, promised to retain traction on just about any surface imaginable and to soften bumps without requiring a suspension.

Earlier this year, I had the chance to try out my first ultra-fat tire electric bike . Unfortunately, it was also my first mountain bike frame and the first folding frame I had tested. There were so many new things about the experience that it was tough to evaluate which aspects of the ride (good and bad) were due to the product and which were due to my unfamiliarity with the bike's features.

In an attempt to get a better perspective on things, I will be spending this spring riding a dedicated ultra-fat-tire e-bike, a dedicated folding e-bike, and a dedicated mountain e-bike. First up: the $1,500 Velotric Nomad 1 , which falls in the ultra-fat tire category.

Enlarge / Aerial view/solar panel floating in the dam. (credit: SONGPHOL THESAKIT )

The cost of solar power has dropped dramatically over the past decade, making it the cheapest source of electricity in much of the world. Clearly, that can mean cheaper power. But it also means that we can potentially install panels in places that would otherwise be too expensive and still produce power profitably.

One of the more intriguing options is to place the panels above artificial bodies of water, either floating or suspended on cables. While more expensive than land-based installs, this creates a win-win : the panels limit the evaporation of water, and the water cools the panels, allowing them to operate more efficiently in warm climates.

While the potential of floating solar has been examined in a number of places, a group of researchers has now done a global analysis and find that it's huge. Even if we limit installs to a fraction of the surface of existing reservoirs, floating panels could generate nearly 10,000 TeraWatt-hours per year, while keeping over 100 cubic kilometers of water from evaporating.

Enlarge / In Texas, solar facilities compete for space with a whole lot of nothing.

Earlier this week, the US' Energy Information Agency (EIA) gave a preview of the changes the nation's electrical grid is likely to see over the coming year. The data is based on information submitted to the Department of Energy by utilities and power plant owners, who are asked to estimate when generating facilities that are planned or under construction will come online. Using that information, the EIA estimates the total new capacity expected to be activated over the coming year.

Obviously, not everything will go as planned, and the capacity estimates represent the production that would result if a plant ran non-stop at full power—something no form of power is able to do. Still, the data tends to indicate what utilities are spending their money on and helps highlight trends in energy economics. And this year, those trends are looking very sunny.

Big changes

Last year , the equivalent report highlighted that solar power would provide nearly half of the 46 Gigawatts of new capacity added to the US grid. This year, the grid will add more power (just under 55 GW), and solar will be over half of it, at 54 percent. In most areas of the country, solar is now the cheapest way to generate power , and the grid additions reflect that. The EIA also indicates that at least some of these are projects that were delayed due to pandemic-induced supply chain disruptions.