Electrifying rural and remote off-grid locations: Why LPG power plants are ideal
Combining gas turbines and an Organic Rankine Cycle, Heat ReCycle offers a compact solution for stand-alone energy requirements. Siemens Energy manager Wolfgang Klink takes us on a short walk in the woods to demonstrate why the use of LPG fuel makes this solution ideally suited for power generation in rural or remote off-grid areas.
By Chris Findlay
It is a cold, sunny spring morning in Erlangen, Germany. I’m due to talk with the Siemens Energy manager in charge of Heat ReCycle, a flexible and efficient gas-powered plant solution, about its suitability for meeting the energy requirements of remote communities and others who require robust, affordable distributed electricity supply. But what’s unusual about today’s meeting is the dress code.
It’s a rare occasion when the interview partner requests outdoor clothing and sturdy boots. However, Wolfgang Klink has decided we’ll do things differently today. Instead of a conversation in his office, we are going for a short hike. He’s come prepared, with a backpack and camping equipment, the purpose of which will soon become clear.
“Sometimes, you have to leave the comfort zone of your familiar environment to find inspiration and rethink the most pressing challenges,” explains the wiry, energetic engineer as we head for the forest. “And when the challenge involves providing energy for remote sites, it’s especially fitting to get away for a bit.”
" Already today, more than one billion people lack access to electricity, especially in remote locations that have no links to energy infrastructure. "
Power for isolated communities
En route, Klink gives a rundown of global issues that require solutions: “By 2050, the global population is set to increase by 25 percent – that’s 2 billion people! At the same time, average life expectancy will reach 82 years, and 70 percent of humankind will be living in cities.” These trends are compounded by climate change and the growing global demand for power.
“Already today, more than one billion people lack access to electricity, especially in remote locations that have no links to energy infrastructure, such as islands,” Klink notes. “That’s a major obstacle to development in terms of education, healthcare, or access to global markets.”
In response to these challenges, Klink and his team have developed a solution based on a simple, but ingenious and proven technology. “Two years ago, we elaborated a concept for a small, decentralized power plant with a performance range of 20–100 megawatts that is efficient, economical, and resource-friendly. After evaluating a number of concepts, we decided on a combination of industrial and aeroderivative gas turbines with an Organic Rankine Cycle,” he explains.
Flexibility by design
The result, Klink explains as we reach a small clearing in the trees, is Heat ReCycle, a compact power plant ideally suited to the requirements outlined above. “Let me show you what I mean,” he adds and produces a small portable stove from his backpack, together with a pressurized propane container of the kind that can be purchased at any gas station and is commonly used for barbecue cookers. Within a few minutes, we are sipping hot tea – a welcome energy source on this chilly day – and Klink is explaining the basic concept of Heat ReCycle.
“The first component is a gas turbine that burns Liquefied Petroleum Gas (LPG), such as the propane we are using here,” Klink says. “The advantage of this inherent flexibility is that LPG is a widely available energy source used in households, as a car fuel, or for industrial applications. As you can see, it’s easy to transport. It’s also much cleaner than the reciprocating engines running on diesel or heavy fuel oil that often provide power in off-grid locations. These require more maintenance and cause higher emissions.” Gas turbines, he adds, are not only flexible and have a higher power density – which means that gas turbines need less space for the same power output – but also have longer operational life-spans than diesel generators.
The second element is an Organic Rankine Cycle (ORC) unit attached to the turbine’s exhaust. Instead of water, the ORC unit vaporizes an organic fluid as the heat exchange medium. The hot heat-transfer medium is routed to the ORC turbine to drive the turbine and spin an electric generator for additional power generation. The remaining energy is extracted in a heat exchanger called regenerator, preheating the heat-transfer liquid. The air-cooled condenser cools down the medium to the required conditions, and it is then pumped back to the waste-heat-recovery unit to start the same process over again.
" The advantage of this inherent flexibility is that LPG is a widely available energy source used in households, as a car fuel, or for industrial applications. As you can see, it’s easy to transport. "
More than 2 billion people live in water-scarce areas. Water scarcity is a global challenge high on the UN’s agenda. “We need to use water as delicately as possible,” Klink points out. “This is why water-free operation is a significant benefit in many remote locations or developing countries: Unlike a water-steam cycle, the ORC element completely eliminates the need for water.”
This, together with its fuel flexibility, makes Heat ReCycle ideally suited for less-developed and off-grid areas where importing fuel is expensive and where cost and efficiency are crucial factors to consumers who would otherwise have to rely on inefficient delivery and generation solutions with high emissions.
The flexibility of Heat ReCycle also makes it a good choice for industrial assets that are remotely located or especially energy-intensive – a case in point being cement factories. These are often located far from densely populated areas, and – in addition to the reliability of the power supply – energy costs are a major factor. “Another business case exists in cold regions with subzero temperatures,” Klink adds. The heat-transfer medium or ORC medium freezes at a much lower temperature than water in a steam cycle, and remains liquid down to minus 80 degrees Celsius, while the sealed, self-contained design of the ORC element makes for low maintenance and can even be designed for unmanned operations.
Seeing the forest for the trees
“Heat ReCycle offers attractive investment and operational costs compared to other technologies in the 20- to 100-megawatt range and allows operators to take advantage of low levelized cost of energy,” says Klink. Looking ahead, he is confident that its fuel flexibility makes Heat ReCycle a future-ready solution: “We are committed to retrofitting existing turbines to use zero-carbon or carbon-neutral gas generated with renewables, such as green hydrogen. This means our solution is future-proof.”
We pack up our camping stove and head back to the car, not forgetting the little blue propane canister that embodies the main advantages of Klink’s ingenious solution – its simple, compact design; its cleanness and efficiency; and above all its versatility in using various types of fuel that are readily available and transportable.
It is said that sometimes, you can’t see the forest for the trees; but sometimes, there’s a simple solution staring you right in the face.
Apr 7, 2020
Christopher Findlay is an independent journalist specializing on technology and business reporting. He lives and works in Zurich, Switzerland.
Combined picture credits: Uwe Mühlhäußer
An ORC array uses an organic fluid characterized by high molecular mass (e.g., silicon fluids, hydrocarbons, or refrigerants) and a lower boiling point than water as a heat-transfer medium. This is evaporated in a boiler to convert industrial exhaust heat into mechanical energy and then electricity before passing through a heat exchanger for recondensation.
Because it operates at comparatively low temperatures, an ORC is especially effective for heat recovery in combination with gas-powered turbines, as well as concentrated solar power, biomass, or geothermal plants. Unlike a conventional combined cycle power plant, this hermetically sealed cycle does not require water, making it a good choice for arid locations.