On-Site Power, Sized to the Site
GRECO generates behind the meter, so a campus does not wait years in an interconnection queue. Which machine does the generating is decided by scale and by what a site can actually be permitted for — solid oxide fuel cells below roughly twenty megawatts, combined cycle gas turbines above it. Either way the heat is recovered and sold.
51–61% Electrical Efficiency
Net efficiency on natural gas that beats a simple-cycle turbine outright, and holds at tens of megawatts rather than needing hundreds.
90%+ Total Efficiency
High-grade stack heat recovered into district energy lifts total fuel efficiency past ninety per cent.
Near-Zero NOx
No flame means the reaction that forms nitrogen oxides never occurs — the single biggest permitting advantage on an urban site.
Modular by Design
Capacity is added in stacks as load arrives, instead of committing to one oversized machine and running it at part load for years.
Scale Decides the Machine
These are not competing preferences. Below roughly twenty megawatts a fuel cell holds its efficiency where a turbine cannot, and permits in places a flame will not. Above it, the combined cycle’s second stage pays for itself. Drag the load and watch which one wins.
Efficiency holds at small scale, so a 20 MW plant is not penalised for being small. Modular: capacity is added in stacks as load arrives.
Bands are indicative. Real selection also weighs fuel supply, air permitting, noise limits, heat offtake and phasing — which is the conversation rather than the slider.
How a Solid Oxide Stack Works
The whole case rests on one fact — nothing is set alight.
Scroll the diagram sideways to see it all.
Schematic of the conversion path, not a simulation. Layers are drawn touching because in a real cell the electrolyte is a thin membrane between the two electrodes.
Nothing is set alight. Natural gas is reformed to hydrogen-rich gas at the anode. Across a ceramic electrolyte held at roughly 700–850 °C, oxygen ions migrate from the cathode and combine with that fuel. The reaction releases electrons directly as electric current, leaving water, carbon dioxide and heat.
The consequences follow from that one fact. Without a flame there is no high-temperature nitrogen reaction, so NOx is near-zero rather than something to be scrubbed. Without rotating machinery there is little noise and little to wear out. And because the efficiency does not come from the size of a turbine, a twenty-megawatt plant is not penalised for being small.
The heat is the second product. Stack temperature is high enough that recovered heat lands well above the 50 °C a fourth-generation district energy network needs, so it can be sold rather than rejected. An Energy Transfer Station forms the metering boundary.
And Where Scale Justifies a Turbine
On a large regional campus the arithmetic changes, and combined cycle is the right answer.
Generating twice from the same fuel
A gas turbine burns fuel to spin a generator, then its 500–600 °C exhaust passes through a heat recovery steam generator to raise steam that drives a second turbine. That recovered second cycle is the whole point: it lifts net electrical efficiency to 60–64%, where a simple-cycle turbine manages 35–42%. H-class machines exceed 64% — the highest of any thermal cycle in commercial operation.
What it asks for in return
Scale, land and an air permit. Combined cycle wants roughly 50 MW and up to justify the second stage, takes three to four years from order to operation, and burns fuel — so NOx abatement and dispersion modelling are part of the application rather than a footnote. On a regional site with room and a grid connection to displace, that is a reasonable trade. Beside housing, it usually is not.
What behind-the-meter power actually means
The phrase describes where the generator sits relative to the utility meter — and that position changes everything downstream.
In front of the meter, a generator sells into the grid and the campus buys back from it — which means the campus still needs an interconnection, still joins the queue, and still waits. Behind the meter, the generation sits on the customer side: electrons go straight to the load without transiting the utility's network at all. That is why on-site power generation collapses a five-to-seven year wait into months. The campus is not asking for grid capacity, so there is nothing to queue for.
It also changes the economics. Behind-the-meter generation avoids transmission and distribution charges entirely, because the power never uses those assets. On a load running continuously at high utilisation, that delivery component is a large share of the bill — and a data centre is close to the ideal case for it, because it runs flat and around the clock.
The usual objection is that this abandons the grid. It does not. A behind-the-meter campus can stay connected for backup and can bid demand response — and a load that never requested firm capacity in the first place is one the utility does not have to build for. In a constrained system, the most useful thing a large new load can do is not join the queue.
Why Generate On Site
Four constraints decide whether a campus can be built where the demand actually is.
The interconnection queue
New transmission service for a large load runs five to seven years across much of North America. Generation on the customer side of the meter does not join that queue.
Urban air permitting
A combustion plant in a populated area is an air-quality argument before it is an engineering one. Without a flame, that argument largely disappears.
Noise in a neighbourhood
Fuel cells have no combustion and no large rotating machinery, so they run quietly enough to sit beside housing — which is where the heat customers are.
A fuel decision left open
The same stacks take natural gas now and hydrogen later. Nothing about the plant has to be rebuilt to change fuel, because there is no burner.
Where the Heat Goes
Every one of these turns a cost into a revenue line.
District energy
Recovered heat is lifted to 50 °C a fourth-generation neighbourhood network needs and metered across an Energy Transfer Station.
Absorption cooling
High-grade heat drives absorption chillers, converting recovered thermal energy back into cooling and taking electrical load off the plant.
Controlled-environment agriculture
Greenhouses beside a campus buy winter heat directly, and the same site can supply the CO₂ they would otherwise have trucked in.
Process heat
Industrial neighbours take steam or hot water that would otherwise come from a dedicated boiler on their own site.
The Supplier Landscape
Solid oxide is a commercially deployed technology with an established manufacturing base.
Bloom Energy
The largest deployed base of solid oxide power in North America, with published platforms running natural gas and hydrogen and a growing data-centre footprint.
Doosan / HyAxiom
Long-running Korean fuel-cell business supplying utility and commercial stationary power, with grid-scale installations in operation.
Elcogen
European cell and stack manufacturer supplying integrators, with an explicit focus on data-centre applications.
Named for market context only. Equipment is selected per site against load, fuel supply and permitting; naming a manufacturer here does not imply a supply agreement.
How It Reads Against Net Zero
Efficiency rather than offsets
Converting fuel at 51–61% electrically, and over 90% once heat is sold, means less fuel burned per useful unit of energy delivered — before any accounting treatment is applied.
Local air quality
Near-zero NOx and SOx addresses the pollutant that actually governs whether a generation plant can be permitted near housing, distinct from the carbon question.
Hydrogen without a rebuild
A plant that already runs on hydrogen when supply exists avoids the stranded-asset problem of combustion equipment specified for a single fuel.
Heat treated as a product
Recovered heat sold into district energy displaces gas boilers elsewhere in the neighbourhood, so the emissions benefit reaches past the fence line.
Said plainly
Running on natural gas, this is a lower-carbon and dramatically lower-pollutant way to make electricity — not a zero-carbon one. What it does is cut fuel per useful unit delivered, remove the local air-quality objection almost entirely, sell the heat instead of rejecting it, and leave the fuel decision open so that hydrogen requires no rebuild. We would rather state that than call it clean.
Solid oxide fuel cells: common questions
Sources & Further Reading
Talk to us about on-site generation
Tell us the load, the site and the timeline, and we will tell you what can actually be permitted and built there.