Multi-Use Roof Eliminates Roof

September 11, 2025 by Bryan Cockfield 55 Comments

One of the biggest downsides of installing solar panels on a rooftop is that maintenance of the actual roof structure becomes much more difficult with solar panels in the way. But for many people who don’t have huge tracts of land, a roof is wasted space where something useful could otherwise go. [Mihai] had the idea of simply eliminating traditional roofing materials altogether and made half of this roof out of solar panels directly, with the other half being put to use as a garden.

Normally solar panels are installed on top of a roof, whether it’s metal or asphalt shingles or some other material, allowing the roof to perform its normal job of keeping weather out of the house while the solar panels can focus on energy generation. In this roof [Mihai] skips this step, having the solar panels pull double duty as roof material and energy generation. In a way this simplifies things; there’s less to maintain and presumably any problems with the roof can be solved by swapping out panels. But we would also presume that waterproofing it might be marginally more difficult.

On the antisolar side of the roof, however, [Mihai] foregoes the solar panels in favor of a system that can hold soil for small garden plants. Putting solar panels on this side of the roof wouldn’t generate as much energy but the area can still be useful as a garden. Of course we’d advise caution when working on a garden at height, but at least for the solar panels you can save some trips up a ladder for maintenance by using something like this robotic solar panel scrubber.

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The Sense And Nonsense Of Virtual Power Plants

September 2, 2025 by Maya Posch 32 Comments

Over the past decades power grids have undergone a transformation towards smaller and more intermittent generators – primarily in the form of wind and solar generators – as well as smaller grid-connected batteries. This poses a significant problem when it comes to grid management, as this relies on careful management of supply and demand. Quite recently the term Virtual Power Plant (VPP) was coined to describe these aggregations of disparate resources into something that at least superficially can be treated more or less as a regular dispatchable power plant, capable of increasing and reducing output as required.

Although not actual singular power plants, by purportedly making a VPP act like one, the claim is that this provides the benefits of large plants such as gas-fired turbines at a fraction of a cost, and with significant more redundancy as the failure of a singular generator or battery is easily compensated for within the system.

The question is thus whether this premise truly holds up, or whether there are hidden costs that the marketing glosses over.

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The Confusing World Of Wood Preservation Treatments

August 29, 2025 by Maya Posch 19 Comments

Wood is an amazing material to use around the house, both for its green credentials and the way it looks and feels. That said, as a natural product there are a lot of microorganisms and insects around that would love to take a few good nibbles out of said wood, no matter whether it’s used for fencing, garden furniture or something else. For fencing in particular wood treatments are therefore applied that seek to deter or actively inhibit these organisms, but as the UK bloke over at the [Rag ‘n’ Bone Brown] YouTube channel found out last year, merely slapping on a coating of wood preserver may actually make things worse.

For the experiment three tests were set up, each with an untreated, self-treated and two pressure treated (tanalized) sections. Of the pressure treated wood one had a fresh cut on the exposed side, with each of the three tests focusing on a different scenario.

After three years of these wood cuts having been exposed to being either partially buried in soil, laid on the long side or tossed in a bucket, all while soaking up the splendid wonders of British weather, the results were rather surprising and somewhat confusing. The self-treated wood actually fared worse than the untreated wood, while the pressure treated wood did much better, but as a comment by [davidwx9285] on the video notes, there are many questions regarding how well the pressure treatment is performed.

While the self-treatment gets you generally only a surface coating of the – usually copper-based – compound, the vacuum pressure treatment’s effectiveness depends on how deep the preservative has penetrated, which renders some treated wood unsuitable for being buried in the ground. Along with these factors the video correctly identifies the issue of grain density, which is why hardwoods resist decay much better than e.g. pine. Ultimately it’s quite clear that ‘simply put on a wood preserver’ isn’t quite the magical bullet that it may have seemed to some.

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Avocado Harvester Is A Cut Above

August 26, 2025 by Bryan Cockfield 7 Comments

For a farmer or gardener, fruit trees offer a way to make food (and sometimes money) with a minimum of effort, especially when compared to growing annual vegetables. Mature trees can be fairly self-sufficient, and may only need to be pruned once a year if at all. But getting the fruit down from these heights can be a challenge, even if it is on average less work than managing vegetable crops. [Kladrie] created this avocado snipper to help with the harvest of this crop.

Compounding the problem for avocados, even compared to other types of fruit, is their inscrutable ripeness schedule. Some have suggested that cutting the avocados out of the trees rather than pulling them is a way to help solve this issue as well, so [Kladrie] modified a pair of standard garden shears to mount on top of a long pole. A string is passed through the handle so that the user can operate them from the ground, and a small basket catches the fruit before it can plummet to the Earth. A 3D-printed guide helps ensure that the operator can reliable snip the avocados off of the tree on the first try without having to flail about with the pole and hope for the best, and the part holds the basket to the pole as well.

For those living in more northern climates, this design is similar to many tools made for harvesting apples, but the addition of the guide solves a lot of the problems these tools can have which is largely that it’s easy to miss the stems on the first try. Another problem with pulling the fruits off the tree, regardless of species, is that they can sometimes fling off of their branches in unpredictable ways which the snipping tool solves as well. Although it might not work well for avocados, if you end up using this tool for apples we also have a suggestion for what to do with them next.

Converting A Sprinkler System To DC

August 22, 2025 by Bryan Cockfield 14 Comments

Famously, Nikola Tesla won the War of the Currents in the early days of electrification because his AC system could use transformers to minimize losses for long distance circuits. That was well before the invention of the transistor, though, and there are a lot of systems that still use AC now as a result of electricity’s history that we might otherwise want to run on DC in our modern world. Sprinkler systems are one of these things, commonly using a 24V AC system, but [Vinthewrench] has done some work to convert over to a more flexible 24 VDC system instead.

The main components of these systems that are set up for AC are solenoids which activate various sets of sprinklers. But these solenoids can take DC and still work, so no major hardware changes are needed. It’s not quite as simple as changing power supplies, though. The solenoids will overheat if they’re fully powered on a DC circuit, so [Vinthewrench] did a significant amount of testing to figure out exactly how much power they need to stay engaged. Once the math was done, he uses a DRV103 to send PWM signals to the solenoids, which is set up to allow more current to pull in the solenoids and then a lower holding current once they are activated.

With a DC power supply like this, it makes it much easier to have his sprinkler system run on a solar powered system as well as use a battery backup without needing something like an inverter. And thanks to the DRV103 the conversion is not physically difficult; ensuring that the solenoids don’t overheat is the major concern here. Another great reason to convert to a DIY sprinkler controller is removing your lawn care routine from an unnecessary cloud-based service.

$A photo of a large warehouse with many skylights and windows near the roof. In the middle of the image extending out into the distance are hundreds of grey refractory bricks stacked on top of a smaller set of brown bricks stacked on top of pallets. There appear to be rails on the floor of the warehouse and small dollies underneath the pallets.$

Thermal Batteries For Lower Carbon Industrial Processes

August 20, 2025 by Navarre Bartz 39 Comments

Heating things up is one of the biggest sources of cost and emissions for many industrial processes we take for granted. Most of these factories are running around the clock so they don’t have to waste energy cooling off and heating things back up, so how can you match this 24/7 cycle to the intermittent energy provided by renewables? This MIT spin-off thinks one solution is thermal storage refractory bricks.

Electrified Thermal Solutions takes the relatively simple technology of refractory brick to the next level. For the uninitiated, refractory bricks are typically ceramics with a huge amount of porosity to give them a combination of high thermal tolerance and very good insulating properties. A number of materials processes use them to maximize the use of the available heat energy.

While the exact composition is likely proprietary, the founder’s Ph.D. thesis tells us the bricks are likely a doped chromia (chrome oxide) composition that creates heat in the brick when electrical energy is applied. Stacked bricks can conduct enough current for the whole stack to heat up without need for additional connections. Since these bricks are thermally insulating, they can time shift the energy from solar or wind energy and even out the load. This will reduce emissions and cost as well. If factories need to pipe additional grid power, it would happen at off-peak hours instead of relying on the fluctuating and increasing costs associated with fossil fuels.

If you want to implement thermal storage on a smaller scale, we’ve seen sand batteries and storing heat from wind with water or other fluids.

A fisheye lens picture over the Junma Solar Power station in the Mongolian desert. There is a large image of a horse made out of solar panels in the image. A sunset is visible in the upper right of the image, but most the picture is brown sand where there aren't dark blue solar panels.

China’s Great Solar Wall Is A Big Deal

August 18, 2025 by Navarre Bartz 60 Comments

Data centers and the electrification of devices that previously ran on fossil fuels is driving increased demand for electricity around the world. China is addressing this with a megaproject that is a new spin on their most famous piece of infrastructure.

At 250 miles long and 3 miles wide with a generating capacity of 100 GW, the Great Solar Wall will be able to provide enough energy to power Beijing, although the energy will more likely be used to power industrial operations also present in the Kubuqi Desert. NASA states, “The Kubuqi’s sunny weather, flat terrain, and proximity to industrial centers make it a desirable location for solar power generation.” As an added bonus, previous solar installations in China have shown that they can help combat further desertification by locking dunes in place and providing shade for plants to grow.

Engineers must be having fun with the project as they also designed the Guinness World Record holder for the largest image made of solar panels with the Junma Solar Power Station (it’s the horse in the image above). The Great Solar Wall is expected to be completed by 2030 with 5.4 GW already installed in 2024.

Want to try solar yourself on a slightly smaller scale? How about this solar thermal array inspired by the James Webb Telescope or building a solar-powered plane?