Technology About Gas

Gas as a bridge

 By Robin Wylie
About gas

Natural gas is inexpensive, reliable and flexible. Furthermore, you do not need to provide for any storage capacity. Natural gas is also an environmentally friendly energy source whose burden on your installation is minimal: clean, easy to use and highly efficient. The applications of natural gas are as numerous as they are powerful. For example the history of Kuraymat power plant, in Egypt, explains perfectly the role of natural gas as a perfect bridge toward a low carbon and renewables future…

(Cover Photo by www.indiatimes.com)

The Kuraymat power plant sits in an uninhabited patch of desert around 100 miles (160 kilometers) south of Egypt’s capital, Cairo, just east of the River Nile. It’s a natural gas plant, but with one significant difference.

Kuraymat is one of a new generation of power plants, called Integrated Solar Combined Cycle (ISCC) plants, which use a combination of high-efficiency natural gas generators and solar energy to generate electricity.

Alongside the plant’s two natural gas electricity turbines is a field of 160 “solar troughs” — linear arrays of inwardly curved mirrors which track the sun throughout the day, harnessing the abundant solar energy of the Sahara.

The troughs are spread across an area of more than 6,458,346 sq ft (600,000 sq m), and focus the sun’s rays onto fluid-filled pipes, generating steam which is subsequently used to power a turbine that generates electricity in tandem with the plant’s natural gas turbines.

Its sprawling solar collectors allow the Kuraymat plant to produce 20 MW of additional power on top of the 140 MW produced by its natural gas turbines. In total, the plant can supply enough electricity to power 500,000 homes with electricity 24 hours a day. What’s more, the addition of the solar troughs saves between approximately 9,000 and 15,000 tons of CO2 per year.

The Kuraymant plant, and the various other ISCC plants which have been constructed around the world in the past decade, demonstrate the changing role of natural gas in the energy sector, and its potential to act as a “bridge” towards a low-carbon future.

The solar trough portion of the Kuraymat ISCC plant, Egypt. Credit: Green Prophet

It might seem paradoxical to advocate the use of a fossil fuel in order to reduce CO2 emissions, but in fact natural gas is uniquely placed to facilitate the necessary transition from our coal-dominated, carbon-intensive present to the low-carbon future which, most of the world now accepts, humanity must eventually adopt.

Despite being a fossil fuel, natural gas — a blend of gaseous hydrocarbons dominated by methane — has always been a relatively green source of energy next to the more carbon intensive hydrocarbons such as coal and petroleum. In the transport sector, for instance, adopting methane-based fuels can cut CO2 emissions by20-25 percent compared to traditional fossil fuels such as petrol and diesel.

But natural gas could have a far greater impact on humanity’s carbon footprint when used as a means of electricity generation. In this context it has by far the lowest carbon footprint of all fossil fuels, producing around half the CO2 emissions of coal — still the planet’s main source of electricity generation — per kwh of generated electrical power.

Concerns over “fugitive” methane emissions, which can be associated with natural gas production and lead to higher GHG emissions, are well justified. However with appropriate monitoring measures at the point of production, such emissions can be minimized. Moreover a comprehensive 2011 report by Deutsche Bank found that, even after accounting for fugitive methane emissions, US natural gas-fired electricity generation still produced 47 percent fewer GHGs than coal.

The importance of natural gas

The USA — the world’s second largest producer of electricity behind China — has been moving away from coal in favor of natural gas in recent years (the so-called “shale revolution”). In 2015 natural gas overtook coal to become the country’s primary source of electric power generation for the first time ever.

Until relatively recently, Europe was heading in a similar direction. Between 1992 and 2008, natural gas-powered electricity production rose year-on-year in the EU, and at the end of that period very nearly overtook coal as the continent’s leading source of electricity generation.

But since 2008, electricity generation from natural gas has fallen sharply across Europe. And while the renewable sector has soared to become the EU’s leading source of electricity (a phenomenal achievement) coal power generation has remained relatively unchanged. By following the US example and beginning to phase out coal power generation in favor of natural gas, Europe could significantly reduce its CO2 emissions with relative ease.

But while eschewing coal for natural gas could cut carbon emissions significantly in the short term, there is an overwhelming global consensus that renewable sources of energy must eventually come to dominate if we are to minimize the impacts of man-made climate change.

That’s why Kuraymat, and other plants like it, could be so important. The capital intensive nature of renewables means that it is not feasible for them to completely replace other forms of energy like coal power at this stage. But by constructing hybrid plants which marry together renewables with natural gas, carbon emissions can be cut relatively quickly, while also allowing the renewables sector to grow in tandem.

 

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Furthermore, solar power capacity can be built more economically if constructed as part of solar-fossil hybrids such as ISCC plants, meaning that such hybrid plants could provide a pathway to implementing and maturing solar at lower costs than standalone (“greenfield”) installations. For instance, a 2015 study by researchers at Duke University found that ISCC reduces the levelized cost of concentrated solar power-generated electricity by 35-40 percent relative to a stand-alone plant.

The combination of natural gas and renewables also makes sense from a supply standpoint. The intermittent nature of solar and wind power (which can also be hybridized with natural gas electricity generation with relative ease) means that a backup supply of power must be present in order to integrate such sources stably into electricity grids. Natural gas, with its extreme flexibility, makes sense as a partner in this sense, too. In this light, the expansion of hybrid natural gas and renewable energy power plants like the one at Kuraymat could provide an ideal bridge towards a renewable-dominated future.

That vision remains some way off, however, ISCC plants have seen significant growth in the past decade. As well as the Kuraymat plant, which became operational in 2011, numerous other ISCC plants have been constructed worldwide — unsurprisingly in similarly sun-drenched locations.

The first major ISCC plant to become operational was the Martin Next Generation Solar Energy Center, located in southern Florida, in late 2010. Operated by Florida Power and Light, the plant combines a 75 MW concentrated solar power system — the world’s largest — with a much larger natural gas component, producing a combined output of 1150 MW.

Other ISCC plants currently in operation include the Ain Beni Mathar plant in Morocco (20MW), the Hassi R’Mel plant in Algeria (20MW) and the Yazd plant in Iran (17MW).

The few ISCC plants which are currently in operation might not amount to much in terms of offsetting global CO2 emissions, but they stand as an important proof-of-concept for ISCC technology, and underscore the potential of natural gas to help accelerate the decarbonization of the energy sector.

 

about the author
Robin Wylie
Freelance earth/space science journalist. Currently finishing off a PhD in volcanology at University College London.