Gas Turbine Technology: Reaching the peak

Turbine inlet chilling technology offers a simple, but effective solution to satisfy the GCC’s demand for peak power, says TAS.

We have seen the numbers. Regional power demand growth is averaging 7-10 per cent. To make these numbers jump to real life all you have to do is go for a drive in Dubai, Abu Dhabi or Manama and look at all the construction cranes. They’re too numerous to count.

Development is proceeding at a breakneck pace, and so it seems, is demand for power. The new commercial office complexes, apartment towers, hotels and resorts, low-rise housing developments, shopping malls, and the urban infrastructure supporting this unparalleled growth, will need power. Lots more power.

Given the times we live in, the Cooperation Council for the Arab States of the Gulf (GCC) has an unprecedented opportunity to demonstrate global leadership in the efficient growth of power generation infrastructure. The region has already achieved leadership recognition in the comfort cooling market by embracing district cooling as an “infrastructure approach” that reduces power demand by up to 40 per cent. As evidenced by the recent International District Energy Association (IDEA) conference in Abu Dhabi, the region is clearly embracing energy efficiency as its primary driver. Both the infrastructure approach and supporting technologies are widely embraced on the demand side of the region’s unprecedented growth.

Work with what you have

Before the industry starts spending billions in building new power plants, the first question to ask is whether it can increase production and efficiency from the current fleet of generation assets? This is the principal of economic efficiency – Make current assets more productive and more environmentally friendly.

Just as the region is embracing district cooling to help manage growth in power demand, generation asset owners are asking the question: What can we do to boost generation capacity and operating efficiency from current assets? This is a critical question to ask, given the level of GCC construction activity and that up to 60 per cent of a large building’s electricity usage is attributed to air conditioning load.

Most of this demand occurs during the summer months as outdoor temperatures rise. During this period, average daily temperatures can range from 27 à‚°C to 41 à‚°C, with daily highs (Dubai) often reaching 45 à‚°C in August.

For the largest country in the region, Saudi Arabia, summer temperatures can vary significantly. In the coastal regions of the Red Sea and Persian Gulf, relative humidity can rise above 85 per cent and frequently reach 100 per cent for extended periods of time. The average summer temperature is 45 à‚°C, but readings up to 54 à‚°C are common. At this temperature, the Arabian Peninsula can be one of the hottest regions on the planet.

The preferred generation technology to support highly variable peak demand is combustion turbine (CT) – both simple and combined-cycle. No other power generation technology is as reliable or cost effective in supporting peak power demand, which requires the flexibility to ramp up and down following the load patterns over the course of any given day.

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Gas turbines are the preferred technology to support peak power, but are still not an ideal solution. As is well known within the industry, CTs derate as outdoor temperatures rise. They lose power in direct proportion to the increase in outdoor air temperature. Derating impacts all gas turbines with an average output loss of 20 per cent, with some turbines being impacted more than others.

Arresting the degradation

To help address the degradation effect, CT power augmentation technologies have been developed to help restore combustion turbines to full capacity during peak demand periods. These technologies are categorized as turbine inlet cooling or turbine inlet air cooling in which all available solutions serve the same purpose – cooling the inlet air. Turbine inlet chilling is recognized as the most robust of the inlet cooling technologies as it maximizes power output for any given CT asset and works well in high relative humidity conditions, which are common to the coastal and more populous regions of the GCC.

Turbine inlet chillers address the critical problem of combustion degradation
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A final argument in favour in working with existing assets is that inlet chilling technology on a $/MW and $/MWh basis costs less. Turbine inlet chilling capacity can be built for approximately $200-250/kW compared to a new simple cycle CT at minimally $400/kW, at design conditions. Maximizing the economic value current plant should be the first consideration as plant operators evaluate your options in adding incremental peak capacity.

Maximize asset productivity

High heat and humidity conditions are ideal for turbine inlet chilling technology as the use of chillers in cooling the inlet air empowers plant operators with the ability to fool Mother Nature. Plant operators can programme the chiller system to cool the inlet air into the turbine to a specific inlet temperature, thereby maintaining full control over the weather. Plant operators can turn the chillers up or down, based on the target MW output for the day, hour or even 15-minute intervals. Thus, plant operators can set and maintain MW output as a constant level by having full control over inlet air temperatures. Only inlet chilling offers this degree of control.

Turbine Air System (TAS) is widely recognized for introducing the concept of pre-engineered, modular, and factory constructed chilled water systems to the power generation industry. This approach to standardize product design and manufacturing is described as packaging, in which most components are assembled in a factory controlled setting environment versus on-site in the field. TAS standard products designs are customizable and engineered to maximize overall system efficiency, which helps ensure an attractive return on investment for asset owners.

The concept of maximizing efficiency in power generation is not new. In high growth markets like the GCC, companies such as TAS are seeking to extract the hidden MWs that remain untapped in the gas turbine power generation fleet. A noteworthy comparison to hidden MWs would be with another source of energy, such as oil.

At a certain price point it makes sense to open wells that were previously capped because of low global crude prices. It is now time to uncap the region’s CTs and extract their full value as a latent power generation asset.

Peak demand is likely to grow more rapidly in the GCC than in any other region of the world. A worthwhile comparison would be the peak demand growth in the city of Los Angeles (LA). In LA, peak demand is growing at approximately 8 per cent per year. This in itself is a remarkable figure, but with many of the world’s construction cranes now concentrated in Dubai, growth in power usage is running at 15 per cent and set to remain high.

With projected peak demand forecasts, the time has come to leverage and maximize the region’s existing base of CT assets. Economically and operationally speaking, it simply makes sense. Operationally, it also makes sense. CTs are among the most energy efficient generation options for producing reliable peak power. Nuclear is base load only, coal is slow to ramp up, wind and solar are difficult to schedule and to varying degrees much less reliable as a source of peak power. Peak capacity must have the inherent flexibility to meet the daily needs of grid operators in matching supply to demand, even in intervals as short as 10 or 15 minutes.

Chillers allow plant operators to set and maintain output at a constant level
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As we look at the rapid development and projected population growth for the region, turbine inlet chilling also makes sense environmentally. For instance, CT technology is considered one of the most environmentally friendly of the peak generation fossil fuel sources. Turbine inlet chilling, when installed on a combined-cycle CT, takes on and slightly improves the environmental characteristics of that CT.

Combined-cycle heat rates remain essentially the same with the addition of inlet chilling, and as compared to a new aeroderivative simple cycle peaker, carbon dioxide emissions per MWh are approximately one half the output. On a turbine inlet chilled combined-cycle plant, NOx emissions are essentially 50 per cent of the emissions of a new aeroderivative peak power plant.

In an era in which emissions caps and carbon trading are beginning to move from concept to reality, it only makes sense to evaluate, and quantify, the environmental benefits, or costs, associated with generation asset investment decisions.

Efficient growth is smart growth

On the demand side of the power equation, companies and technologies are already leading the way to increase energy efficiency by proactively managing the need for incremental peak power. As related to the power generation industry and the GCC’s continued need for air conditioning, adequate and affordable sources of peak power capacity are essential to the region’s continued growth. As they same say in the GCC: “air conditioning is not a luxury; it is a necessity.”

TAS understands this, and, in its continued pursuit of high efficiency power generation technologies, offers a cost effective, easy to site, more environmentally friendly source of peak power.

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