Stirling System May Yet Prevail

Financial Times : June 14 2010

By Peter Marsh

Take the ideas of an obscure 19th century Scottish vicar, add a dash of new thinking from the submarine, Formula One and chemical industries - and apply the mix to the requirements to find new sources of energy that are independent of fossil fuels.

This is the recipe for a new business that could produce annual revenues of up to $4bn (£2.75bn) within a few years, according to NTR, a privately-owned Irish company.

While NTR has its roots in operating toll roads in Ireland, in the past few years it has moved into large energy projects. It has now put almost $200m into an effort to become a big manufacturer of plants making electricity by harnessing power from the sun.

The first fruits of this work are almost entirely in the US - where the company is working on two big power projects worth a total of $3.4bn.

But NTR’s ideas could lead to new business opportunities in India as well as parts of Europe and Africa.  NTR is controlled by Tom Roche, a publicity-shy Irish businessman.

It gained a foothold in the solar field through a $100m purchase two years ago of the majority share in Stirling Energy Systems, based in Scottsdale, Arizona.

SES has been working since the 1980s on ways to commercialise the ideas of the Rev Robert Stirling.

In 1816, Stirling devised a blueprint for a high-efficiency “heat machine” to rival James Watt’s steam engine.

Yet while Stirling’s invention has gained a worldwide legion of enthusiastic followers, no one has built a commercial Stirling system capable of being made in high volumes and operating reliably, without the need for a lot of maintenance.

This is in spite of massive efforts by companies as diverse as the Ford automotive business and the Dutch electronics group Philips to make the exotic technologies behind Stirling systems work effectively.

But now, thanks to $80m of development effort since SES was acquired, plus the support of two big automotive parts companies that have agreed to help in the manufacturing of the engines, NTR hopes Stirling systems are at last about to become mainstream products.

“We feel the challenges to manufacturing Stirling engines on a large scale have been overcome,” says Ian Simington, head of NTR’s solar division, who is also SES’s chairman.

He says that the Stirling-based projects offer “big advantages” over rival systems for using energy from the sun to generate electricity.

Such systems are either based on photovoltaic cells or on other forms of “solar thermal” designs similar in principle to the SES technology.

One rival type of solar-thermal design - which has been used in most of the installations so far that use this basic technology - is the so-called “tower system”.

In this, moving mirrors built in large fields focus the sun’s energy onto a single large collector located in a centrally positioned tower.

“We think we’ve brought down capital and operating costs to below those used in other types of solar plants,” says Mr Simington.

He says that the high inherent efficiency of a Stirling machine - of up to 25 per cent, compared with 15 per cent for most car engines - makes Stirling-based systems fairly cheap to run so long as the engineering problems can be ironed out.

Also - because the SES engine does not require a boiler to create steam, often used in rival solar thermal designs - it avoids the use of water, which is normally in short supply in the hot parts of the world most favoured for solar energy. Tower systems, for instance, have steam turbines as an essential part of their design.

SES’s technology is based on focusing the sun’s rays via large parabolic dishes, similar to those used in satellite communications, onto a series of Stirling engines that then convert the energy into electricity.

Each dish has an accompanying engine at its central point to make a combined dish/engine set that will cost about $70,000 to manufacture in high volumes, according to SES’s plans.

The first large-scale evidence of SES’s ambitions is a $20m pilot plant on the outskirts of Phoenix in Arizona that was built last year and paid for with the help of US government grants.

The installation comprises 60 dish/engine sets and can produce 1.5MW.

In the pipeline are two much bigger commercial-scale plants - both in California - that are modelled on the same technology. They are set to produce 300MW and 850MW respectively and cost a total of $3.4bn.

The plants have been ordered by San Diego Gas & Electric and Southern California Edison, two large utilities.

Construction of both plants is due to start within the next year, assuming final approvals are gained for financing and planning.

Copyright The Financial Times Limited 2010.