For mobile power applications, diesel is often the fuel of choice in remote regions although there is an increasing demand for alternative fuel sources. We spoke with Ben Van Hove, VP Marketing at genset manufacturer Atlas Copco, about the current and future viability of diesel as a genset fuel, and what other options are available for mobile gensets.
Q: What fuels do Atlas Copco`s gensets currently run on? Are there dual-fuel options?
A: We offer a large containerized genset where dual fuel is an option, so it can use diesel or natural gas or any mixture of both. We typically reconvert it in the factory from a basic diesel engine. We do this for larger gensets because they would typically go on medium- to long-term rentals for IPPs in remote locations; sometimes they have a natural gas supply, or they would like to run on biofuel.
The advantages of a fuel mixture include better transient behaviour; at peak load or startup the gensets can run on diesel so they can better cope, while in stable running conditions they can switch to natural gas. This is an on-demand application, as is reconversion. We`re looking into some versions with natural gas in larger power modes, above 300 kVA. We also see demand for mobile natural gas-fired gensets.
Q: What measures are necessary to adapt gensets to run on alternative fuels?
A: Natural gas is not always the same in different regions. We`re always tweaking and fine tuning, but basically you get the gas, dry it, filter it, whatever, then compress or expand it depending on the pressure you get it with. A pre-treatment system is mounted on the gas train before you can use it in injection, then modified to the injection system and controls to get the mixture right between diesel and gas. On the engine itself there are some changes in terms of measuring and controlling temperatures and vibration. We do natural gas, biogas, diesel and biodiesel.
Things we don`t do: HFO, which is used more and more in some countries that have it available, but it`s not only very corrosive but also very difficult to store and treat. For mobile applications we don`t see the benefit. Flare gas, when treated, is basically natural gas, and we use landfill gas because, when treated, it then becomes natural gas quality. We don`t use it untreated.
Q: What kinds of alternative fuels are preferred in which markets?
A: An interesting point about the energy landscape of the future is that everybody knows we`re going to see a wide variety of solutions that will play somewhere in this new puzzle of energy sources. All kinds of solutions: some say hydrogen, some say fossil fuels, some say we will see biomethane or landfill gas. For us, it`s basically about what is widely available to the customer, which is really the driver for us. For the time being it`s still 70%-80% diesel, but in some areas we see an increasing requirement for natural gas.
Q: What are the advantages and disadvantages of diesel as a genset fuel?
A: It`s important to realize that our main application for gensets is mobile prime power, meaning that the main target niche we focus on with diesel generator sets is rental applications or mobile applications. Diesel generator sets move a lot from one location to the other. Of course if you move your genset around a lot it`s also very important that you have fuel available in most places, so therefore in mobile applications diesel still is the prime fuel used in backup gensets. That said, we do see an increasing demand for natural gas-driven gensets.
The first advantage of diesel is that it`s widely available. The second is that, within a certain engine frame size or module, the power density is higher with diesel than with natural gas; also for transient behaviours, startup or loads, diesel engines are faster to react. On the contrary, the advantage of gas is that it`s cheaper per kW and burns more cleanly (if you forget about aftertreatment; you get a very similar level of emissions with aftertreatment). Other fuels, such as biodiesel or biogas, are very similar. Biodiesel is basically the same as diesel, it burns in the same way, and biogas is treated in the same way as natural gas.
For us diesel is still the primary source, although we do see increasing demand for natural gas or biofuel gensets. It`s regional, more from stationary applications, which you typically see in the US and Canada. In Europe we see less of that demand, although there is some of course; again there is high demand in stationary applications, and also in applications where there is combined heat and power (CHP) demand. In mobile applications we see very little of that demand.
Oil-producing countries, such as Nigeria and countries in the Middle East, prefer to export the oil they find and keep the natural gas. Gas is a waste product for these oilfields and is very hard to transport if there`s not the right infrastructure, so they prefer to convert it into fuel they can more easily transport.
Q: Are other fuels likely to replace diesel in the foreseeable future?
A: We definitely don`t see a replacement for diesel in the foreseeable future. There will be some pieces of the puzzle eaten by other fuels, but in our applications diesel will remain the primary source of energy.
Q: What about the difficulties involved in transporting diesel fuel?
A: Diesel is a liquid that needs to be transported with certain precautions, but the world has learned how to transport it well enough. Gas is much more complicated to transport. In general, diesel is still one of the easiest-to-transport fuels there is. There are environmental concerns with spillage, but with all of our machines being spillage-free and having double-walled fuel tanks we can solve this challenge very well.
Also, this is where extra efficiency elements come in. In the past you had to refill a genset maybe every day, but that`s far from the case now so, in remote areas, you only need to refill it maybe once a week, maybe even less. Our focus is very much on using the least amount of fuel possible, as opposed to switching.
And instead of having one big genset that runs all time, a lot of smaller ones share the load and become a lot more efficient. There are lots of ways that we can reduce our fuel consumption, which is as important as changing the type of fuel. You can save a lot more CO2 by making installations more fuel efficient rather than changing the primary type of fuel.
Q: What percentage of the genset market do you think will switch to alternative fuels in the foreseeable future?
A: In the US with shale gas, it depends a lot on where it`s coming from and how it`s being handled, but we see in some of the oil & gas applications where they have waste gas available that, with some simple treatments, they can be used to generate excess electricity and transport it off the site. Because of the very low-cost abundance of gas, countries like Nigeria have oil produced for export and keep the natural gas for local energy production. Of course everything changed a bit in the last 18 months with the strong reduction in oil per barrel price, so I think interest in alternative fuels was bigger two years ago than it is today. Diesel has become a very economical fuel nowadays. But that might change again in the future â€“ how are we to predict fuel prices?
One driver for that is also the complexity of the emissions legislation regarding diesel engines. It`s very complex in North America, and by 2020 we will also see that in Europe. Diesel engines will become ever more regulated, and then alternative gases could well have an increased place in the market. Something to watch for in the next two to three years.
Q: What are Atlas Copco`s plans to increase the fuel flexibility of its gensets?
A: Different gases and fuels are always being looked at. But, the challenge is still to get the message out about the modular power plant concept and the best way to put diesel driven compressors together to run efficiently â€“ efficiency is the keyword that drives us here, and is more of a focus.