Decentralized Energy, North America, On Site Power

Preventing blackouts

  • spend billions on new wires; this won’t completely eliminate blackouts and will exacerbate other problems
  • save money by encouraging decentralized energy; this will greatly reduce system vulnerability and deliver a host of other benefits.

DECENTRALIZED ENERGY COULD HAVE PREVENTED BLACKOUT

Years of active discouragement of all local power by the Ohio and Michigan utilities left the grid vulnerable to sagging voltage. Local generation can alter its output automatically to support voltage and enable lines to carry full design power.

In neighbouring Indiana, NiSource encouraged local power at the steel mills that it serves. It formed an unregulated subsidiary in 1994 that invested over US$300 million in 460 MW of decentralized power. The subsidiary, Primary Energy, built five projects that recycle waste heat and normally flared blast furnace gas. All of the power is consumed at the steel mills, easing transmission congestion and supporting local voltage.

The Indiana steel mills collectively save over $100 million per year by producing power with waste energy

Had the Ohio and Michigan steel mills recycled energy to produce on-site power, the plants would have supported the voltage and allowed the wires to carry more power to other consumers. All other things equal, the blackout would not have occurred.

Furthermore, such actions are good for the economy and the environment. The Indiana steel mills collectively save over $100 million per year by producing power with waste energy. These decentralized energy projects produce no incremental emissions and displace the emissions of a medium-sized coal-fired station operating around the clock. They are the environmental equivalent of roughly 2500 MW of new solar collectors operating for 20% of the time, on average.

These projects have not hurt the local utility, Northern Indiana Public Service Company, on balance. Yes, the utility sells less electricity to the mills, but steel production has risen, requiring more shifts and pumping up the local economy, increasing other electricity sales.

Decentralized energy (DE) has come of age. It employs proven central generation technologies and fuels but is located next to electricity and thermal loads. DE power goes directly to users, by-passing transmission, and DE plants recycle normally wasted heat, saving fuel and pollution. Local generation options are technically ripe, environmentally superior, and at least twice as efficient as average central generation.

Essential for optimizing power output

Power plants operate in every conceivable environment, each with its own filtration challenges. Here, Richard P. Dunn and James A. Benson address some of those challenges and discuss how proper filtration can keep turbines running at optimal efficiency levels.

Today there is growing awareness of the contribution to sound turbine-operating practice that is provided by a well maintained air filter system. Simply put, turbine air filtration plays a huge role in the power plant’s performance. When the air that flows through the turbine is clean, it helps the turbine to generate as much power as possible in the given conditions.

The three most common problems that dirty air can create for a turbine are:

  • blade erosion
  • compressor fouling
  • plugging of cooling passages on the blade.

These conditions cause the turbine’s efficiency to suffer, which reduces energy output and eats power plant profits.

TURBINE FILTER BASICS

Turbine air filters should be designed to balance two important objectives: filtration efficiency and minimal pressure drop. Power plants require the turbine to use as small a portion of its energy as possible to pull the air through the system. Therefore, air filters must remove as many contaminants as possible (filtration efficiency) without impeding airflow (pressure drop), allowing more turbine energy to be used for producing power.

The need for balance is perhaps best understood when dealing with filtration extremes. For example, a sheet of steel provides fantastic filtration efficiency because no dirt passes through it, but unfortunately the air is blocked as well. On the other hand, a fish net doesn’t restrict airflow a bit, but its filtration efficiency is terrible. The ideal filtration system provides a balance between these seemingly conflicting goals of high filtration efficiency and low pressure drop.

PARTICLES ARE SMALL – BUT NOT HARMLESS

Although dust and other air particulates are very small in size, they can do great damage to turbines. Turbine blades are designed and shaped to create very precise aerodynamic flow patterns. Anything that interferes with this aerodynamic flow can cause the turbine to work harder and lose efficiency.

Turbine rotor assemblies are large (generally 1.5-1.8 metres in diameter) and they spin very fast (several thousand rpm). Recognizing that damage will occur when dust particles hit the blades over and over again at that speed, it is understandable that filtration becomes a very important part of protecting and maintaining the turbine’s performance.

Figure 1 illustrates the relative sizes of common dust components and particles.