Carbon Commentary newsletter. Fortnight ending 20th July 2025

1, Solar penetration and negative wholesale prices. The second quarter of the year was good for solar production across Europe. Total production was over 100 TWh. In June, PV delivered more electricity than any other source. But one consequence of the growth in solar is increasingly frequent negative hourly prices. Over the course of the first six months of the year, Spain experienced 459 hours of below zero prices, or about 10% of the entire period, while the Netherlands saw just over 400 hours. Montel, the analytics firm that produced these figures, expects the boom in negative prices to continue this summer as solar PV output remains strong. Of course in time electricity users will get better as adjusting their demand to maximise power use in times of negative prices but so far Montel sees little sign of flexibility in energy use as renewable electricity surpluses flood into the European market. (Thanks to Raymond Betz).

2, Electric trucks. A German manufacturer reported the successful use of 6 MAN trucks to transport its timber products over long distances. One vehicle regularly completes a 650 km trip overnight. The company says that these heavy electric trucks use about 80-90 kWh per 100 km, or about 10% better than the average for the 200 trucks pre-released by MAN prior to the start of full production this year. The increasingly obvious viability of electric heavy vehicles underlies the recent change in scenario projections from the UK’s high voltage system operator. NESO now projects that only 60% of all trucks greater than 26 tonnes will use hydrogen in 2050, down from 100% in its 2024 projections. My guess is that next year will see another fall in this number, with the changed forecast partly driven by the evidence of rapidly growing penetration of heavy electric vehicles in China where they already represent 13% of new sales compared to 1 or 2% in the West.

3, Direct air capture (DAC). Most current forms of DAC require large amounts of energy to drive off CO2 from the chemicals that have initially captured the gas. New techniques may avoid some of this energy burden. Germany’s Phlair said that it would build a plant that will grow to 500,000 tonnes of DAC built alongside the Northern Lights CO2 terminal in Norway, thus linking it directly to large-scale geologic storage. The Phlair approach is to use an alkaline solution to absorb CO2. Then acid is added to create a neutral fluid, resulting in the CO2 leaving the solution. This carbon dioxide is transferred into storage. The key Phlair innovation is then to use a proprietary device (a type of hydrolyser) that recreates the separate alkaline and acid chemicals used in the first steps. The company claims the result is an energy efficiency three times better than conventional DAC technologies such as those used by Climeworks. Perhaps as importantly, the hydrolyser does not need to operate continuously, meaning the machine can benefit from periods of low electricity prices. (See note 1).

4, Perovskite efficiency. I wrote enthusiastically about the prospects for the use of perovskites in solar PV in 2016. Progress has been much slower than I expected - largely because it has been very difficult to ensure a long operating life for the panels - but my guess is that we will eventually see tandem cells with perovskite sprayed on top of silicon as a cost-effective alternative to conventional PV. In the US, CubicPV claimed a new world record of 24% efficiency at converting the energy from the sun into electricity in a small PV module. All credit is due for the achievement. However other companies have boasted of higher efficiencies: Oxford PV, for example, published a figure of 26.6% last year and a few days ago Longi said it had achieved 33.9% for a single cell. (Efficiencies at the individual cell level will be slightly higher than those of a module)

5, Google buys more low carbon electricity. Google said it has contracted with hydro-electric owner Brookfield to take up to 3 gigawatts of power from its dams in the eastern US. This is one of the increasing number of deals that seek to secure low carbon electricity for datacentre use. But is this contract really going to avoid extra CO2 emissions? If Google buys all the electricity coming from the dams, existing customers will have to purchase their power from other sources. In all probability these replacement generators will use fossil fuel, implying that the overall effect of Google’s increasing power needs will be to add to emissions. Google and Brookfield try to get around this point by claiming that as a result of the contract the dams will be ‘relicensed, overhauled, or upgraded to extend the asset’s useful life’. I’m not convinced: if Brookfield ccould make money from extending the operating period of the dams, it would have done so whether or not Google bought the power. The company needs to build its own solar or wind farms to show its expansion is truly carbon neutral.

6, Floating solar. A Malaysian utility said it would develop a 100 MW solar plant on the largest lake in southeast Asia, which also provides the water for a 400 MW hydro-electric plant. If successful, the PV could be extended to up to 2.2 GW, making it by far the largest floating solar project. Merging a hydro-electric plant with PV makes obvious sense: the hydro can provide power when the sun is down.

7, Off-grid green ammonia. Another illustration of the increasing Chinese leadership in the energy transition. Envision celebrated the commissioning of an off-grid green ammonia plant using wind as the energy source with grid-forming batteries and liquid nitrogen as the main storage medium. (I presume liquid nitrogen is used because nitrogen is needed for the production of ammonia so it can serve two purposes). AI is used in combination with detailed weather forecasting to ensure that the electrolysers can work all hours. At full planned capacity, this plant will eventually produce about half a percent of world ammonia needs.

8, Sustainable fuels. Prometheus Fuels, a US startup backed by BMW and Maersk amongst other funders, announced it was ready for commercial production of fully carbon neutral liquid fuels. The press release said ‘We’ve invented and built an integrated DAC (direct air capture) and fuel synthesis system that captures carbon from the air, runs on renewable energy, and produces e-Fuels that cost less than fossil at scale’. I don’t know whether Prometheus is genuinely capable of offering methanol or gasoline at prices below today’s levels but its technology does appear to represent a huge advance on the complicated routes that other liquid fuels are taking. It won’t need to use green hydrogen, for example.

9, Brickmaking using ammonia and hydrogen. Making bricks requires high temperatures of up to 1100 degrees Celsius and results in about 1% of global emissions. Even with advances in generating heat with electricity, achieving these temperatures currently requires the use of natural gas. A Fraunhofer-led project in Germany showed that bricks can be made using the heat generated by combustion of a mixture of ammonia and hydrogen. Despite the claim in the media report, this wasn’t the first example of successfully using an alternative to natural gas: a UK manufacturer recently experimented with 100% hydrogen in a government-funded project. However the new German study identified a possibly cheaper route to decarbonisation that would use imported ammonia as the primary energy source.

10, Enhanced rock weathering (ERW). Some types of rock absorb atmospheric CO2 relatively rapidly when ground into fine dust and spread thinly over fields. This can also help fertilise the land by adding trace amounts of useful nutrients such as phosphorus. For quarry owner Sunrock in North Carolina with mountains of basalt rock dust to get rid of, this an easy choice. It partnered with Lithos Carbon, an organiser of ERW projects, to spread dust across agricultural land in the state. Other owners of mines with basalt waste will follow.

11, Carbon dioxide removal (CDR). Frontier is a fund that invests in CDR on behalf of its large corporate backers by pre-buying defined tonnages of carbon dioxide. Among several recent deals, it bought future carbon capture tonnage from Limenet, an Italian company that takes limestone (calcium carbonate) and turns it into lime (CaO) and then calcium hydroxide (CaOH). The CaOH is then turned into a solution of calcium bicarbonate which is stable in seawater and which reduces ocean acidity, enabling more CO2 to be stored in the water. 50% of the calcium hydroxide remains and can be used to capture CO2 directly from the air. This seems to be a clever, simple, near-universal and potentially cheap route to direct air capture combined with improvements in ocean storage of CO2.

Thank you for the messages over the last couple of weeks. I do apologise for not replying to them all.