Renewables create a tail wind for aeroderivatives, GE believes

While GE’s market outlook for large frame heavy duty gas turbines is certainly not what it was – and not helped by a current oxidation issue affecting the first stage blade of HA and 9FB machines – Martin O’Neill of GE Power Services believes “there are reasons to be bullish about gas”, not least as a replacement for retired coal and nuclear units, and, within the gas segment, “a lot of reasons to be excited about aeroderivatives”, which “play very nicely into current market conditions”, which he characterises as “complex and dynamic.”

Indeed, he says GE is “doubling down in this space”, as evidenced by the recent announcement of a $200 million investment in the aeroderivative business over the next three years. This investment will be across new product introductions, notably the LM9000 (derived from the GE-90 engine employed on Boeing 777s and capable of 75 MW, with very high power density), as well as the LM6000 PF+ and LM2500+G5 engines. It will also provide for further development of aeroderivative services, including repowering of LM and non-LM machines (an aeroderivative version of the recently launched Cross-Fleet initiative targeting other OEM’s heavy duty gas turbines, see MPS, July 2018) and upgrades of the GE LM fleet. The latter includes, for example, increased reliability/availability and enhancement of revenue opportunities resulting from even faster start up times and integration with batteries (the Hybrid Electric Gas Turbine offering).

A key focus of the investment is further expansion of capabilities at the Houston Service Center, Jacintoport – GE’s largest centre serving the LM fleet – aiming at faster turnaround of machines, improved shop flow, and development of digital capabilities, enabling the facility to service more than the current 500 engines and modules per year.

Renewables, a key driver

The rise of intermittent renewables is a key driver behind the enthusiasm for aeroderivatives, creating a burgeoning demand for flexible, fast-start, rapid-ramping peaking capacity for balancing and firming the grid.

“We love renewables”, says Aman Joshi, general manager of the aeroderivative gas turbine segment within GE gas power systems. He notes that a number of countries (eg, Australia, Germany and India) are reaching what he calls a “tipping point”, recognising they need simple cycle fast start peaking capacity to support renewables (and to provide the inertia of rotating masses to the grid) and coming to the realisation that they “can’t have renewables without fast start”– resulting in a “tremendous tail wind” building up for aeroderivatives.

GE quotes a Technavio study that shows the aeroderivative gas turbine market growing at about 5% annually between 2016 and 2020, with aeroderivatives “likely to become the go-to technology to provide balancing services for renewable energy.” 

The need for peaking power to support renewables plays to the strengths of aeroderivative gas turbines, with their aviation pedigree making them very well able to cope with cycling and frequent start-stops without maintenance penalty and able to ramp up very quickly (currently five minutes from “cold metal to 100% full power”, but with plans afoot to reduce this substantially, to just two minutes) – enabling them to participate in ancillary services markets. This operational flexibility is coupled with high power density (about 7x that of recips, meaning reduced footprint and increased transportability), high efficiency, including at part load (with, for example, 40% efficiency at 50% of full power), low emissions, deep turndown capabilities, and high availability/minimal downtime, with a focus on condition based maintenance (again stemming from the aviation heritage), a modular structure facilitating repair, and fast component change out. Aeroderivatives, which can be truck mounted (TM2500), also lend themselves to rapid deployment. Aman Joshi refers to the case of Myanmar, where theleadtime“fromcontracttoelectronson the grid was 45 days.”

Improving performance

The growing role for aeroderivatives in grid support further emphasises the need for improved performance, greater flexibility and reductions in costly down time for maintenance and repairs. These are among the areas targeted by the new investment, not just for the GE fleet, but also looking to repower (ie replace) machines supplied by competing OEMs, which GE calls “Cross- Fleet repowers”. The company reports that it is currently executing a $15 million order for a Cross-Fleet repower, expects another such order before year end and four more next year, while in the past it has carried out aeroderivative repower projects on Siemens, Rolls-Royce and Pratt & Whitney units in several countries, including Jamaica, Australia, the Netherlands, as well as on an offshore platform in the North Sea. On the rationale for extending the Cross-Fleet concept to the aeroderivative market, Martin O’Neill asks rhetorically: “why would we not offer a GE machine and the benefits of our highly competitive service network” to owner/operators of other OEM machines?

For the LM stationary power fleet (amounting to about 2700 currently operational units worldwide, total installed capacity over 60 GW) GE offers an engine exchange programme (with several financing and leasing options) as an alternative to overhaul of an existing ageing engine, resulting in a reduced shutdown period, with the old engine replaced with a new, overhauled, or partial life engine – requiring an outage of a mere 2 to 3 days.

One recent example is a project just completed at COMETA’s wood-based panel plant in Soria, Spain. The cogen facility at the plant employed an LM2500 Base SAC gas turbine, with 100 000 running hours on the clock and due for a major overhaul/ repair. In lieu of overhaul, the owner opted for a new LM2500 Base SAC gas turbine via the engine exchange programme. Among the benefits to the owner: asset life reset to zero hours; 2% output increase; 3% heat rate improvement; 1% increase in electrical efficiency; and just one outage instead of several, with less impact on availability. Increased operational flexibility of the new engine was also a benefit: “We needed an upgrade that provided us with more flexibility to balance the intermittent nature of the power grid”, said José Luis Lázaro, deputy general manager, Losán Group, owner of COMETA.

As well as engine exchange and repower, GE offers a range of additional upgrades to optimise the operation of aeroderivative units (see table, p 26), including addition of a battery to create what GE calls the Hybrid EGT (Electric Gas Turbine). Southern California Edison has been operating two such Electric Gas Turbine hybrids for about a year, each consisting of 10 MW/4MWh battery plus upgraded LM6000 gas turbine, and the result has been substantial fuel savings and around 50% fewer gas turbine starts.

The battery of the Hybrid EGT produces immediate power when needed, giving time for the gas turbine to start up. The ability to supply power essentially instantaneously on demand enables the facility to earn revenue as a provider of ancillary services such as spinning reserve.

GE’s planned reduction in aeroderivative start up time to two minutes will allow deployment of a smaller battery, reducing costs.

“Renewables and batteries are disruptors, but are generally good for aeroderivatives”, says Martin O’Neill.

Recips vs turbines

Reciprocating engines are also capable of very fast starts and can be integrated with batteries. A November 2018 white paper (GE Aeroderivative Gas Turbines, by John Ingham and Monamee Adhikari) addresses the recip vs turbine issue (and will be the subject of a future article).

The white paper, which aims to set out the advantages of aeroderivatives that “reciprocating engines can’t match” notes that aeroderivative gas turbines are “potentially more reliable and may have a higher availability than reciprocating engines (98.2% vs. 93% availability, according to ORAP), meaning they could be a more sensible investment for grid firming” and points out that over half of GE’s global aeroderivative fleet has “demonstrated a 100% reliability rate and over 98% availability rate, under certain specific conditions and with appropriate fuel.”

The white paper also notes that all of GE’s aeroderivative gas turbines have at least two separate shafts, one shaft providing the necessary air flows and the other driving the generator. “What this means, in practice, is that in case of a frequency drop in the grid, the other shaft can quickly increase its speed, and consequently the unit’s power, even while the generator is being slowed down. This results in a much faster response to frequency fluctuations, helping to ensure a much more stable and reliable grid.”

Then there is the issue of generator inertia and its important role in grid stability. The white paper argues that gas turbines operating at 3600 rpm contribute more to system inertia “when compared to reciprocating engines that usually run at 900 rpm. After all, inertia is a result of mass and speed squared, so four times the speed results in 16 times the inertia, for the same size generator.”

GE’s perspective on the relative merits of reciprocating engines vs gas turbines might of course have been somewhat coloured by the fact that, with the sale of its distributed power business, including Jenbacher and Waukesha, to Advent International, and its launch as a standalone entity called INNIO, GE is no longer in the piston engine business.