19,5 miljoen voor windonderzoek

Windenergie

In programma Far and Large Offshore Wind (FLOW) werkt het Delftse instituut voor windenergie Duwind samen met ondermeer energieproducent RWE, onderzoeksinstituut ECN en een aantal industriële partners aan de ontwikkeling van grootschalige windenergie op zee.

De toekenning van bijna 20 miljoen euro betekent voor Duwind dat er op verschillende faculteiten van de TU in totaal zestien promovendi kunnen worden aangesteld, licht prof.dr. Gerard van Bussel toe. Er zal onderzoek plaatsvinden naar andere windturbines, nieuwe funderingstechnieken, onderhoudsstrategieën en installatietechnieken die geschikt zijn voor windparken ver op zee. Ook de inpassing van de stroom in een dynamisch elektriciteitsnet op Europese schaal wordt onderzocht.

“We kunnen nu met de eerste fase van het onderzoek beginnen”, zegt Van Bussel. “De tweede fase gaat pas in nadat een nieuw offshore park gebouwd is, maar nu Bart Engineering de tender heeft gewonnen en niet RWE zal dat nog even op zich laten wachten.”

Gas from coal layers is potentially a huge source of fossil fuel. If half of the coalbed methane (CBM) worldwide could be produced, proven global gas reserves would increase by 20 to 74 percent. For the Netherlands, coalbed methane amounts to an estimated extra 0.6 to 43 percent of the proven gas reserves. Production of coalbed methane is especially strong in the USA, where it accounts for 10 percent of the natural gas production. However, traditional methods produce less than half of the methane available. In 1998 researchers increased gas production by injecting CO2 into a producing CBM field. But, as Patrick van Hemert points out in his thesis, the effect of CO2-injection cannot be predicted because the processes involved are poorly understood.

First: how much methane can be extracted from coal by flushing it with another gas? To determine this, geochemist Van Hemert took a cylinder of (British) coal, dried it in an oven for two weeks, and then applied a vacuum to it for three days, before saturating it with methane for one week under a pressure of 80 bars. After that, the flushing could begin. Van Hemert connected the flushing gas at one end – it flowed through at a rate of just 1 cubic centimetre per hour. Meanwhile, every 30 minutes he analysed the composition of the out-flowing gas at the other end of the coal cylinder. He discovered that flushing can retrieve 88 percent of the stored methane (he worked with nitrogen and hydrogen, as well as with carbon dioxide). But perhaps ‘flushing’ is not the right word, because the gas exchange is a slow process; it took up to 30 days for the gas to diffuse through the 19-centimetre long coal sample.
The exact way in which a gas like CO2 binds to coal is unknown, but not for a lack of ideas. Van Hemert explains that there are three major theories for this process called ‘sorption’: one theory argues that CO2-molecules will fit in between the long coal polymer chains, another proposes that gas molecules will gather in micropores, and the third surmises that gas molecules will simply form a liquid-like layer around the coal. Van Hemert: “If there are three or more theories explaining the same thing, it means the right theory hasn’t yet been found.”

He adopted a ‘back to basics’ approach and built an instrument (a ‘manometric apparatus’) to actually measure sorption, which he does by adding a known amount of gas to the coal sample in the sample cell and then measuring the pressure. After stabilisation, this pressure is typically lower than it would have been without the sample, because of the gas ‘sorbed’ by the coal. The amount of sorption can be derived from the pressure in the sample cell.
The principle may be simple, but the practice is long and hard. The manometric instrument needs to be virtually leak-free because of the small volumes, high pressures and long durations involved (leakage was measured with helium before and after each experiment). After each gas injection the sample needs about three days to stabilise. A typical sorption diagram with 20 points therefore takes two months to complete. This means that not enough measurements could be made to experimentally determine which of the competing theories best describes sorption.

Another unknown is the carbon balance of the process: if you inject CO2 into a coalbed and burn the methane that comes out, you also release CO2 into the atmosphere. So what is the correct balance? Does the climate profit too, or just the gasman? Theoretically, a little more CO2 is stored than methane won. But a better theory is needed to make adequate predictions. 

Patrick van Hemert: ‘Manometric determination of supercritical gas sorption in coal’, received his PhD degree on September 1, 2009, supervised by Prof. Dr. J. Bruining.

Windenergie

Windenergie

Windenergie

In programma Far and Large Offshore Wind (FLOW) werkt het Delftse instituut voor windenergie Duwind samen met ondermeer energieproducent RWE, onderzoeksinstituut ECN en een aantal industriële partners aan de ontwikkeling van grootschalige windenergie op zee.

De toekenning van bijna 20 miljoen euro betekent voor Duwind dat er op verschillende faculteiten van de TU in totaal zestien promovendi kunnen worden aangesteld, licht prof.dr. Gerard van Bussel toe. Er zal onderzoek plaatsvinden naar andere windturbines, nieuwe funderingstechnieken, onderhoudsstrategieën en installatietechnieken die geschikt zijn voor windparken ver op zee. Ook de inpassing van de stroom in een dynamisch elektriciteitsnet op Europese schaal wordt onderzocht.

“We kunnen nu met de eerste fase van het onderzoek beginnen”, zegt Van Bussel. “De tweede fase gaat pas in nadat een nieuw offshore park gebouwd is, maar nu Bart Engineering de tender heeft gewonnen en niet RWE zal dat nog even op zich laten wachten.”

Zie ook de Flow website