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MAN prefers “power-to-gas” as an alternative to new power lines

17 March 2014

The construction of a new north-south electric power line is being extensively discussed in Germany. MAN SE, one of Europe’s leading manufacturers of commercial vehicles, engines and mechanical engineering equipment, and mostly owned by the Volkswagen Group, prefers “power-to-gas” instead. Power-to-gas, or e-gas as Audi calls it, converts surplus electricity into synthetic natural gas and utilizes the existing gas infrastructure. Direct use can be made of natural gas in homes or to drive vehicles. Alternatively, it is also possible to convert it back into electricity with the aid of gas power stations.

Top technical solutions linked to the field of natural gas belong to our core competencies. In view of the existing alternatives, one should consider very carefully whether Germany’s citizens should really be expected to accept the expansion of electric power lines on a massive scale.

— Dr. Georg Pachta-Reyhofen, CEO of MAN SE

Power-to-gas is a system solution designed to store large quantities of electricity produced from renewable sources on a long-term basis and subsequently make it available wherever it is needed without being connected to high-voltage power lines.

In the case of natural gas, MAN offers standard products along the entire process chain. For instance, MAN’s gas engines play a part in supplying decentralized power, especially as a back-up for electricity generated by wind or sun. Combined heat and power plants can generate energy using MAN’s natural-gas engines. Reaching energy conversion efficiency levels of up to 90%, the performance of combined heat and power plants is, in terms of efficiency, higher than that of large conventional power stations which achieve conversion efficiency of no more than around 40%.

Business with natural-gas-powered engines for combined heat and power plants in the 37 to 550 kilowatt range represents MAN’s most profitable and highest-turnover segment in the field of external engines.

MAN’s turbine technology is also relevant. As an example, 6 MW turbine is so compact that it even fits into a double garage, making it highly versatile—serving as a small on-site generator or on remote oil platforms. Solvin GmbH & Co KG, a joint venture between Solvay and BASF, saw its first commercial plant go into operation in fall 2013 with the new MAN gas turbine generation. Through cogeneration (CHP), it produces both heat and electricity – using more than 80% of the energy content of the natural gas employed.

In the form of CNG/biogas engines, MAN also offers clean mobility solutions for urban transport. MAN leads the market in this sector, having already delivered more than 5,000 buses and chassis with CNG engines, their output spanning five levels from 220 to 310 hp. Even without using biogas, the CO2 emissions generated by CNG engines is still some 17% less than in the case of diesel-powered vehicles.

Engines that can utilize liquefied natural gas as fuel are of increasing interest for ocean-going vessels. These engines emit significantly less carbon dioxide and nitrogen oxide than conventional engines burning marine diesel or heavy fuel oil. The American shipping company, TOTE Inc., will be relying on MAN’s dual-fuel engines with gas injection for two new standard-container ships. These two container ships will be the first to be powered largely by liquefied natural gas.

In addition, MAN is also active in the field of natural gas production, e.g. with the aid of underwater compressors. The Group has, for instance, developed the world’s first subsea compressor. These are special compressors which immediately compress gas on the seabed and conduct it into pipelines in a transportable form – a milestone for the entire gas and oil industry. As a result, previously uneconomical reserves can now be exploited.

March 17, 2014 in Brief | Permalink | Comments (11) | TrackBack (0)

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The efficiency of CHP is mentioned, but not that it only applies if the heat is required at that particular moment.  All of this begs the question of where to get the carbon to make the methane, and how much energy overhead is involved.  Mobile uses will dump the carbon back to the atmosphere, adding to the amount requiring re-capture.  I notice that NONE of these news releases ever mentions cost.

The efficiency of the E-gas scheme is even lower than straight hydrogen, and engines far lower than fuel cells.  Unless and until all the RE involved gets compensated purely at market rates (no feed-in tariff), E-gas from RE is going to be horrendously expensive due to all the losses.  Batteries will have a huge cost advantage.  That is something that the E-gas advocates want everyone to forget.

E-gas does 'solve' the renewable energy storage problem, but the conversion losses have got to be horrendous. Germany has gone off the deep end with their energy schemes, but I guess they can afford it (so far, anyway).

They can afford to as long as they are otherwise dependent on Russia for energy.

Note how "MAN" "MAN" "MAN" is all over this article. This scheme is one company's plan to increase its future profits. That alone doesn't make it a 'bad' idea but I'd like to see an independent & unbiased examination.

The most interesting part is the bit about the world's first undersea gas compressors. There is talk of extracting gas intermixed with brine off the Gulf of Mexico. The temperature of the brine is hundreds of degrees. Given the impracticality of sending air undersea to combust,wouldn't geothermal make the scheme work, and even form the basis of an electric grid to complement gas energy?

There have been several proposals for using oil-associated geothermal brines to drive low-temperature vapor engines.  Perhaps these deep-sea systems can use a high-pressure working fluid, such as ethane.

Dr. Georg Pachta-Reyhofen seems to be disregarding the second law of thermodynamics


PS he does seem to be aware of the first law of Politics

@Engineer-Poet

"Batteries will have a huge cost advantage."

Agree batteries are more efficient and better for storing electricity for a short amount of time.

However the one big advantage of power to gas is the cheap cost of storage *capacity*. This makes it useful for seasonal storage. Battery capacity is far to expensive for this.

For example Germany already has a few months worth of natural gas storage. Imagine the cost of storing the same amount of energy in batteries.

Storing energy as gas also has much greater losses.  Hydrogen requires several times the volume to store the same energy as methane and requires major re-work of distribution and consumption systems, but converting power to methane is a lossy step itself.

All of this costs money.  Have you noticed that none of the gushing news pieces about E-gas ever mention price?

All of this grows out of one assumption:  that humanity must rely on the intermittent supplies of the wind and sun, and we have to bank them ourselves against later need.  The assumption is false.  Uranium is continually leached out of rocks by weathering and delivered to the world's oceans at about 32,000 tons per year.  Fission of 1 ton of uranium per year is enough to deliver about 1 GW of electric power, so uranium can deliver roughly 32 TW(e) to humanity into the indefinite future.  Uranium can be mined as required.

Going "forward" by trying to live off diffuse, intermittent energy flows extracted over vast areas isn't even all that environmentally friendly.  The one guaranteed result of the Energiewende is to give Germany a choice between carbon-belching Russian gas and filthier lignite.  We can only pray for sanity to finally come back to Berlin.

Chapter 4 of this thesis - is the only place I've seen capital costs of power to gas mentioned. The variable costs, are mostly those of the electricity input, and depend on the degree of overcapacity of renewables built.

http://www.uni-kassel.de/upress/online/frei/978-3-89958-798-2.volltext.frei.pdf

Hypothetically nuclear is great. However meanwhile the nuclear nations in the west, France, US, and the UK, plan to retire old plants faster, than building new plants, they are all engaged in an unpublicised phase-out. Luckily plenty of renewables are also being built at prices far below new nuclear. These low prices can be attributed to Germany's early aggressive push of renewables.

But keep on betting on your nuclear pony, meanwhile renewables will continue to be built.

Chapter 4 of this thesis - is the only place I've seen capital costs of power to gas mentioned.

A PhD dissertation, not exactly proof of anything (especially the assumptions which went into it).  But there are some very interesting quotes in that Chapter 4, such as page 105:

The necessity to bridge two weeks of wind calms can only be met by long-term storage facilities. So far, the only option available for this purpose was hydrogen. However, hydrogen as storage option is limited due to high costs, security challenges, missing infrastructure and short lifetimes of fuel cells.

In other words, a massive build-out of something to bridge supply gaps is required, and for "renewables" most of those options do not produce a joule of energy themselves.

The gas network is the largest existing storage facility with proven and available technology (Cerbe, 2008). It has a capacity of hundreds of TWh

Yet Germany's natural gas storage cannot carry through even one winter without massive help from continued imports, coal and the remaining nuclear plants.  At 50% conversion efficiency, Germany's 70 GW(e) of grid load burns through about 3.4 TWh of fuel per day.  Add space heat and transport, and "hundreds of TWh" disappears awfully fast.

There's also the question of where you get the carbon for this "renewable power methane".  I look at the diagram on page 106, and it includes... "Fossil fuels".

The energy demand for CO2 extraction from flue gas (biomass or fossil fuels) are far smaller, as the concentration is much higher (about 10%-vol) and not included in the calculation of the energy storage efficiency.

Not exactly legitimate, given that such capture would be mandatory and actual figures for carbon capture from fossil-fired plants are high enough to be very troublesome.

Using atmospheric CO2 reduces the renewable-power-to-methane efficiency by approximately 15% down to 48%.

Less than half.  On to page 111:

After upscaling to a commercial scale of 20-200 MWel by 2020 and later, investment costs are likely to drop below 1000 EUR/kWel and power-to-gas efficiency are likely to rise to 65-68%.

Presumably that does not include atmospheric-capture overhead, so knock that down to 50-53% for a large fraction of the total storage.  The system must be sized for peak generation, not average, and the lower the capacity factor of the generators the bigger the system must be.  By the time you're done, the capital cost of the storage system alone will be several thousand euros per kilowatt, and it's a net absorber of power to the tune of at least 1/3 of each kWh input.  And here's one of the key assumptions in his analysis:

In future power grids, wind power is likely to be very economic and available at 0-2 EUR-cents/kWhel in times of high wind penetration and low residual load.

In other words, he assumes that generators will be paid unsubsidized market prices, not feed-in tariffs.  When is THAT ever going to happen... and who'll ever build a wind farm if it does?  They're currently needing replacement in roughly 20 years, so there's no way off that particular treadmill.

But keep on betting on your nuclear pony, meanwhile renewables will continue to be built.

Only because legislators demand it while hobbling nuclear power or banning it outright.  Nuclear power requires no storage system to capture fickle power flows until needed.  There's no such thing as "two weeks of atomic calm".  And the author has the gall to assume that nuclear's slow ramp rate is a problem.  Does he bother to analyze the economics of his preferred storage systems with excess base-load energy cranking 24/7?  Nope, that's outside the narrow scope of his thesis... and yours.

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