Green Energy

Greenhouse gas emissions have been declining steadily in the EU in recent years, dropping by over a quarter between 1990 and 2019. However, transport is one sector that has bucked the trend, despite advances in technology. Long before city dwellers complained about air pollution and carbon emissions, they moaned about mounds of manure lining the streets and attracting clouds of flies. In the 19th century, horse-drawn vehicles were used to move freight long distances. While carbon emissions were practically non-existent, horse manure was a big sticking point. It topped the agenda during the first International Urban Planning Conference in New York in 1898. Unfortunately, there was no solution to the horse pollution crisis. Eventually, horses were replaced by other modes of transportation made possible by the combustion engine—trading one type of pollution for another. From horses to horsepower It’s been a long ride from there to here. However, the transport sector continues to create a huge amount of pollution, with road transport accounting for around one-fifth of the EU’s total CO₂ emissions. Reducing greenhouse gas emissions from heavy-duty vehicles like freight and refuse trucks, as well as buses and coaches, is a priority. This sector, which is responsible for a quarter of the EU’s CO₂ emissions from road transport, saw emissions rise by 29% between 1990 and 2019. Moreover, emissions from trucks are set to grow as a proportion of the total, said Andrew Flagg, a senior consultant and project manager at Element Energy, part of multinational consultancy firm Environmental Resources Management. This is due to other vehicles being further ahead with low-emission technology, through the likes of traditional electric batteries in cars. “With decarbonization taking place at quite a pace now for cars and buses, the share of heavy goods vehicles in terms of emissions is going to grow,” he said. “So there’s a particular need to accelerate the decarbonization for those vehicles.” But trucks face challenges when it comes to using electric power compared with lighter vehicles. “The problem is that this sector is particularly difficult to decarbonize,” said Flagg. The long distances that trucks need to travel, for example, creates issues for how often batteries need charging, how fast they charge, as well as the available charging infrastructure. Truck batteries can also be heavy and large, affecting the amount of transportable cargo and how far they can travel before they need recharging. Harnessing hydrogen One answer is to use hydrogen power, using a process whereby hydrogen and oxygen gas are fed into a fuel cell to produce electricity. “With the higher energy density with hydrogen, you can have fewer batteries on a truck,” said Flagg. “This enables you to travel those longer distances and cope with the heavier payloads.” Hydrogen-powered vehicles can also rapidly refuel in minutes. “As a fleet operator, you would not want to spend a long time charging a vehicle,” said Flagg. “Hydrogen enables you to refuel much quicker and therefore enables operational flexibility.” While the technology has shown promise, it has so far often tended to be deployed in smaller-scale demonstrations of limited truck numbers, said Flagg. The H2Haul project that he leads plans to take things to the next level by deploying a fleet of 16 new heavy-duty hydrogen fuel-cell trucks. These will be rolled out in Belgium, France, Germany and Switzerland in collaboration with two major European truck manufacturers, IVECO and VDL. The technology’s performance will be assessed by driving the trucks for more than a million kilometers during normal operations. The first trucks will be on the road in the coming months, with all expected to be in operation by the end of 2023. Performance data will then be collected and analyzed. 16 trucks, 6 fueling stations “H2Haul is groundbreaking in that it’s 16 trucks,” said Flagg. “I would say it’s the next step in terms of getting trucks deployed by European manufacturers, upscaling the number of trucks being developed, and deploying fleets in a range of different countries and operating environments.” To demonstrate their viability, H2Haul is also developing six hydrogen fueling stations. Two are already operational in Switzerland, while others are expected in Belgium and France in the coming months, and two in Germany by the end of 2023. Researchers are now employing a similar approach for waste-collection trucks. The REVIVE project is integrating fuel-cell technology into 14 waste trucks operating in real-world conditions for at least two years at a total of 8 sites in Belgium, Italy, the Netherlands and Sweden. With waste trucks, hydrogen technology has tended to be deployed by smaller manufacturers so far, said Dimitri Van den Borre, a project manager at Tractebel Engineering in Brussels, Belgium, and project lead for REVIVE. “What we need is bigger manufacturers stepping into this market,” he said. Waste benefits Using the technology in refuse trucks is expected to have several advantages. One is that they tend to drive a pre-defined route from a single depot. “The vehicles operate within a confined area, and in this early stage of hydrogen rollout such operations are useful because they don’t need a lot of refueling stations,” said Van den Borre. Waste trucks also often run in urban areas with low air quality and are highly visible to the public. This means residents get to experience the benefits for pollution and noise reduction first-hand. Furthermore, organic waste from incinerators can be used to generate hydrogen, creating a circular ‘waste-to-wheels’ model. And excess energy can be used to power other vehicles or industrial applications. At present, REVIVE has five trucks on the road that have driven over 13 500 kilometers in total so far. However, operational data is limited in the early stages and more extensive results are likely to start emerging from next summer, said Van den Borre. Nevertheless, the trucks are performing well. “It’s a nicer driving environment and they produce less noise than conventional waste collection trucks,” he said, adding that drivers have reacted positively so far. “I think in general, they are quite happy with the trucks and the technology. On a technological level, everything is fine and the trucks are doing what they should be doing.” Achieving traction But a variety of challenges remain at this stage of development. Van den Borre listed the lack of regulation and directives on truck maintenance, as well as the limited current number of hydrogen-equipped truck depots as issues. However, the industry has called for a scaling-up, while the EU moved to accelerate hydrogen development in October. Adopting rules to spur alternative refueling infrastructure, MEPs called for hydrogen refueling stations every 100 kilometers by 2028—ramping up a previous target of one every 150 kilometers by 2031. Van den Borre thinks that projects like REVIVE can open the door for bigger initiatives, potentially leading to the market for hydrogen trucks properly taking off within the next decade. But to boost traction for hydrogen-fuel-cell technology in trucks, drivers themselves should not be forgotten, he added. “It’s not just about dropping the truck and the keys with the driver, but getting them involved in the process,” he said. “You have to find motivated people, engage with them early on and set their expectations right.”

Batteries are undoubtedly part of our energy future. Should you put one in your home now to store solar output, manage your energy use and cut costs? It really depends on what you want to achieve.

Studies in 2017 and 2021 identified key motivations for installing home batteries:

• using your own solar energy
• good for environment
• independence from the grid
• saving money.

With these goals in mind, our research suggests it’s hard to justify buying a battery right now on cost savings alone. If other reasons also matter to you, it might be justified.

Using your own solar

More than 30% of Australian homes have solar systems. They typically generate more than is needed during the middle of the day, less than is needed during morning and evening demand peaks, and nothing at night.

If you don’t have a battery, when you need more power than your solar system generates it’s imported from the grid. You can also export surplus energy to the grid and be paid for it.

But, as solar capacity grows, the maximum power new solar system owners are allowed to export is being limited in many locations. And if too many people in your street are exporting, the local voltage will go high and solar inverters will curtail generation.

One way you can avoid curtailment is by shifting some of your energy use to the middle of the day. Significant loads that could be shifted include:

• water heating
• pool pumps
• air conditioning
• appliances such as dishwashers, clothes washers and dryers
• electric vehicle charging.

If you still have surplus generation, it can be stored in a battery and used later to reduce the energy you import from the grid to cover loads you can’t shift. The energy you could transfer via a battery each day will be whichever is the minimum of your excess generation and the amount you normally import. For example, if you have 3 kilowatt-hours (kWh) of excess generation in a day but import only 2kWh to meet your overnight loads, the maximimum energy you can transfer via a battery is 2kWh.

The graph below shows an example of the energy that could be transferred each day of a year, averaged over 40 houses at Lochiel Park, a precinct of low-energy housing in Adelaide.

For these households, a battery with an 8kWh capacity could handle the energy transfer most days. However, the average energy transferred each day is only 4kWh because some days have low surplus generation or low overnight demand. Households with large solar systems and large daily energy imports from the grid can transfer more.

The battery itself will limit rates of charging and discharging. If you are generating more power than it can handle, some of the surplus will be exported or the solar output could be curtailed. If your load is more than it can handle, you will need extra power from the grid.

Environmental benefits

Storing surplus solar energy and using it instead of fossil-fuel energy from the grid will have environmental benefits.

Most home batteries are lithium-ion batteries. Despite concerns about the environmental impacts of a lithium-ion-led energy revolution, efforts are being made to reduce these impacts.

Other ways to reduce environmental impacts without a battery include:

• use less energy, and shift your load to match your clean energy supply
• choose a green retailer or buy GreenPower.

Independence

A 2017 study found nearly 70% of respondents wanted to eventually disconnect from the grid. Remote households have done it for decades, but need large solar systems and large batteries backed up by diesel generators and gas for heating and cooking.

Being connected to a grid has significant benefits. When not generating enough solar power you can get energy from somewhere else. And when generating more than you need, you can send the surplus somewhere else that needs it. Connecting many loads to many generators increases flexibility and efficiency.

A home battery can let you run your home when the grid fails, but you may need extra equipment to isolate it from the grid at such times. Being off-grid means you may also need to manage your battery differently to keep enough energy in reserve to meet your needs during outages.

Saving money

You could use a battery to reduce costs in two ways:

• store surplus solar energy during periods of a low feed-in tariff (the money you receive for exporting energy to the grid), then use it later instead of importing energy when the price is high
• join a virtual power plant (VPP).

Let us explain further.

The cost of electricity varies throughout each day, depending on demand and on available generation. If you have a meter that records when energy is used, time-of-use and dynamic tariffs will allow you to make the most of price fluctuations.

If the difference between your feed-in tariff and your peak import price is 40c/kWh, each kWh of solar energy you store then use during the peak period saves you 40c. The graph above showed an average daily transfer of 4kWh, saving $1.60 per day. But this household requires an 8kWh battery, costing about $9,600. The payback period is over 16 years – beyond the warrantied life of the battery.

In 2017 we simulated battery use for 38 houses with solar to determine the viability and payback period. Each dot in the graph below indicates the payback period for a particular household with given battery size. The horizontal axis shows the annual surplus energy it generated.

The payback period is better for smaller batteries, which cost less, and for houses with larger annual export.

We assumed a price difference of 40c/kWh between import price and feed-in tariff. We also assumed a future battery price of $600/kWh – we are not there yet (unless you can get a generous subsidy).

The other way of reducing the payback period, and supporting the grid, is to join a virtual power plant (VPP). A VPP is a network of home solar batteries from which the electricity grid can draw energy in times of need.

VPP operators typically offer discounts on the battery cost, its management to take advantage of the retail tariffs on offer, and payments for allowing them to use your battery to trade energy on the electricity markets. Subsidies and payments vary across VPPs.

Other options might be a better bet at this stage

Understand why you want a battery before you start looking. There are other options for making better use of your solar generation, getting clean energy and reducing your costs.

If you have a large solar system, high grid imports and can get a good subsidy, or if you just want cutting-edge energy technology, then you might be able to justify a battery.

If you don’t have solar already, the economics of a solar system with a battery can look attractive. But the solar panels will provide most of the savings.

A new tool developed by researchers from The Australian National University (ANU) shows the best locations around Australia that could be used to build new wind or solar farms. The ANU “heat maps” project is aimed at farmers and landholders, who the researchers say are a crucial piece of the puzzle to help accelerate Australia’s solar and wind uptake and help the nation meet its renewable energy targets. The researchers say the area between Goulburn and Lithgow in New South Wales is especially suitable for new clean energy sites because it is well serviced by transmission lines and has good wind and solar resources. Tasmania has plenty of potential for new wind farms along the north coast and on the King and Flinders islands. “In Victoria, the Yallourn district is attractive because of good wind potential and strong existing transmission into Melbourne, plus there’s a need to replace local coal industry jobs. There’s also extensive wind potential west of Melbourne,” Professor Andrew Blakers, from the ANU College of Engineering, Computing and Cybernetics, said. “South Australia has excellent wind and solar potential to the east of the St Vincent and Spencer gulfs, while Queensland’s best wind and solar sites follow the coastal transmission lines north from Brisbane in areas such as Rockhampton and Mackay. “Perth, on the other hand, has an abundance of suitable solar and wind sites close to transmission lines that run from the north and the south of the city.” ANU Ph.D. researcher Cheng Cheng, who was also involved in the study, said the project aims to empower landowners to approach developers directly and negotiate with them to build solar or wind farms on their property. “Access to high voltage transmission lines is essential for solar and wind farms and landholders in windy and sunny areas near existing infrastructure have a valuable economic opportunity,” he said. “Our heat maps are designed to facilitate collective bargaining with developers. This can also assist the solar and wind farm developers by reducing the complexity and time required to gain legal access and community acceptance. “If landowners or local councils are able to access this sort of information and collectively approach developers themselves, it could speed up the development process. Currently, developers approaching individual landowners may face high rejection rates. “Landholders who host solar or wind farms have another drought-proof income source. This is beneficial for farmers, as crops can be grown underneath both solar and wind farms and animals can have access to shade.” Professor Blakers said access to high power transmission lines is the biggest constraint currently facing developers. “Typical power lines cross dozens to hundreds of properties and require complex negotiations with many people. In contrast, solar and wind farms generally fit on one or a few properties. That usually makes an access agreement much easier to negotiate,” he said. “All of the possible sites we’ve identified are near existing and approved high-power transmission lines. “These maps show the relative cost of renewable energy on each 1,000m x 1,000m parcel of land for solar farms and 250m x 250m parcel for wind.” All land in Australia has been divided into different cost categories for solar and wind generation, ranging from Class A to Class E. Professor Blakers said Class A, B and C sites are strongly preferred. More information about relative costs and renewable energy potential for every LGA in each state and territory can be accessed here. The most suitable locations across Australia are highlighted red and less preferred sites are outlined in pink or blue, while unsuitable areas, including urban areas, protected areas and native forests have been excluded from this study and are shown in green. The heat maps use geographic information to identify the best possible locations. Results should be viewed as indicative rather than conclusive.

Organic solar cells could be made even greener by switching the solvents used in their manufacture. Today’s toxic chlorinated solvents can be replaced by plant-derived alternatives without affecting the resulting solar cells’ light-capturing performance, KAUST researchers have shown.

Organic photovoltaics (OPVs) are one of the greenest solar cell technologies, contributing as little as three grams of CO2 equivalent carbon emissions per KW of energy. “However, their fabrication still relies on halogenated solvents that, on top of being linked to reproductive hazards and cancer, are derived from petrochemical processes,” says Daniel Corzo, a Ph.D. student in Derya Baran’s lab, who led the work.

“We wanted to find green alternatives to protect the health and safety of workers when these cells are manufactured at a larger scale and to further reduce the carbon footprint of OPVs.”

Solvents are critical to OPV manufacture as they are the basis of the printable inks that organic solar cells are made from. “These inks require the organic active materials to remain in solution during processing and then crystallize under optimized conditions as the ink dries,” Corzo says. “Solvent choice greatly affects OPV processing and overall device performance.”

The team identified potential alternative solvents by applying a framework called the Hansen solubility formulation. “This methodology measures how similar molecules are to one another based on their molecular interactions,” Corzo explains. “You can select solvents that are alike at the molecular level but have beneficial properties, including reduced toxicity, or that originate from renewable sources.”

The technique revealed that plant-based solvents called terpenes—a group that includes the aromatic oils eucalyptol and limonene—could be suitable replacements. “These solvents can be derived from plant residue, such as eucalyptus leaves or orange peel, or be produced from algae and microorganisms in bioreactors,” Corzo says.

Solvent blends based on these substances proved to be an excellent fit for OPV manufacture. “We obtained solar cells with efficiencies above 16% using terpene-based inks—essentially the same as from chlorinated solvents—but with an 85% lower carbon footprint and with the potential to become carbon negative in the future,” Corzo says.

“We believe that multiple industries and tech developers will benefit from terpene solvent development,” Baran adds. The team has made their findings freely available in an interactive online library for green solvent selection. “This library can go beyond the use of green solvents for organic electronics because terpenes are also used in food and fragrance industries, for instance,” she notes.

The findings are published in the journal Nature Energy.

Today, the Columbia Center on Sustainable Investment (CCSI) at the Columbia Climate School launched two new reports on the roadblocks to and drivers of investment in renewable energy in developing countries.

The first report, titled “Scaling Investment in Renewable Energy Generation to Achieve Sustainable Development Goals 7 (Affordable and Clean Energy) and 13 (Climate Action) and the Paris Agreement: Roadblocks and Drivers,” sheds light on roadblocks and drivers of investment in renewables while distilling solutions from international experience. It clarifies where international and national efforts should urgently be focused to address the deterrents of investment in renewables and enable zero-carbon energy security and prosperity.

The second report, “The Role of Investment Treaties and Investor-State Dispute Settlement in Renewable Energy Investments,” confirms decades of research that legal protections in investment treaties do not have a discernible impact on promoting foreign investment flows, including in renewables. In addition, investment treaties can be extraordinarily costly for states and for the broader policy objective of encouraging investment in renewables.

“It is now even clearer that investment treaties are neither effective nor decisive in attracting investment in renewables to developing countries,” said Ladan Mehranvar, a senior legal researcher at CCSI.

The zero-carbon energy transition is the solution to the 2022 energy crisis and a fundamental part of the solution to the global climate crisis. Even though private markets will be essential to this process, significant changes in governmental policies are required to support the transition. Much of this investment will be cross-border in nature.

CCSI’s reports not only identify the main roadblocks to investment in renewables but also provide actionable recommendations that developing countries should take to ensure access to affordable, reliable, sustainable, and modern energy for all, and to decarbonize their energy systems and economies, with a view to achieving the U.N. Sustainable Development Goals and the objectives of the Paris Agreement.

“We hope these reports are a useful tool for investors, while also supporting developing country policymakers to address the roadblocks in scaling renewable energy investment,” said Martin Dietrich Brauch, lead researcher at CCSI.

The reports offer policy recommendations to unblock investment in renewables in developing countries, including the following:

• International and national financial institutions should develop efficient and adequate debt financing policies to lower upfront capital costs and encourage public and private finance for investment in renewables.
• Developing country governments should build, bolster, digitize, and upgrade the transmission grid and energy storage solutions to reduce the off-taker risk and ensure grid reliability.
• Developing country governments should design fiscal policy tools to orient and support renewables investment, and periodically review and adjust them in light of changed national and global economic realities.
• Instead of negotiating investment treaties, developing country governments should establish robust and stable institutional, legal and regulatory frameworks that promote a mutually beneficial, long-term, flexible, and durable investment climate.
• At the core of their institutional, legal, and regulatory framework, developing country governments should develop ambitious national energy roadmaps.

Engineers in Melbourne have used sound waves to boost production of green hydrogen by 14 times, through electrolysis to split water.

They say their invention offers a promising way to tap into a plentiful supply of cheap hydrogen fuel for transportation and other sectors, which could radically reduce carbon emissions and help fight climate change.

By using high-frequency vibrations to “divide and conquer” individual water molecules during electrolysis, the team managed to split the water molecules to release 14 times more hydrogen compared with standard electrolysis techniques.

Electrolysis involves electricity running through water with two electrodes to split water molecules into oxygen and hydrogen gases, which appear as bubbles. This process produces green hydrogen, which represents just a small fraction of hydrogen production globally due to the high energy required.

Most hydrogen is produced from splitting natural gas, known as blue hydrogen, which emits greenhouse gases into the atmosphere.

Associate Professor Amgad Rezk from RMIT University, who led the work, said the team’s innovation tackles big challenges for green hydrogen production.

“One of the main challenges of electrolysis is the high cost of electrode materials used, such as platinum or iridium,” said Rezk from RMIT’s School of Engineering.

“With sound waves making it much easier to extract hydrogen from water, it eliminates the need to use corrosive electrolytes and expensive electrodes such as platinum or iridium.

“As water is not a corrosive electrolyte, we can use much cheaper electrode materials such as silver.”

The ability to use low-cost electrode materials and avoiding the use of highly corrosive electrolytes were gamechangers for lowering the costs of producing green hydrogen, Rezk said.

The research is published in Advanced Energy Materials. An Australian provisional patent application has been filed to protect the new technology.

First author Yemima Ehrnst said the sound waves also prevented the build-up of hydrogen and oxygen bubbles on the electrodes, which greatly improved its conductivity and stability.

“Electrode materials used in electrolysis suffer from hydrogen and oxygen gas build-up, forming a gas layer that minimizes the electrodes’ activity and significantly reduces its performance,” said Ehrnst, a Ph.D. researcher at RMIT’s School of Engineering.

As part of their experiments the team measured the amount of hydrogen produced through electrolysis with and without sound waves from the electrical output.

“The electrical output of the electrolysis with sound waves was about 14 times greater than electrolysis without them, for a given input voltage. This was equivalent to the amount of hydrogen produced,” Ehrnst said.

The potential applications of the team’s work

Distinguished Professor Leslie Yeo, one of the lead senior researchers, said the team’s breakthrough opened the door to using this new acoustic platform for other applications, especially where bubble build-up on the electrodes was a challenge.

“Our ability to suppress bubble build-up on the electrodes and rapidly remove them through high-frequency vibrations represents a major advance for electrode conductivity and stability,” said Yeo from RMIT’s School of Engineering.

“With our method, we can potentially improve the conversion efficiency leading to a net-positive energy saving of 27%.”

Next steps

While the innovation is promising, the team needs to overcome challenges with integrating the sound-wave innovation with existing electrolyzers to scale up the work.

“We are keen to collaborate with industry partners to boost and complement their existing electrolyzer technology and integrate into existing processes and systems,” Yeo said.