Power Plant Efficiency Parameters

Power plant efficiency is critical to compete in the current power generation market. The demands in power plant efficiency, minimum and maximum loads, power plant start up and shutdown times, plant flexibility are critical for the financial performance of power plants. It is critical that plant operators select the key power plant efficiency parameters to evaluate.

Power plant output is one of the most important and critical parameters of an overall power plant efficiency evaluation. Once power plant electrical output has been determined, it can be corrected to reference conditions to provide a comparison of current plant power output to rated output. This is very important so that contract guarantees can be confirmed and/or changes in power plant efficiency can be tracked over time.

For example, to determine the combined cycle performance several operational parameters need to be considered to estimate properly the corrected combined cycle performance in terms of electrical output.

Since this parameter is intimately tied to the revenue generated by the plant, high precision measurements are required in order to ensure the highest accuracy power plant efficiency.

TGPS uses state-of-the-art precision instrumentation with valid NIST traceable calibration certificates to measure the power plant output.

Heat consumption is the energy (fuel) consumption of the cycle. The ratio of heat consumption to electrical power output is commonly known as the power plant heat rate. This relationship is a measure of the power plant efficiency. This parameter is therefore an indirect relationship of the financial performance of power plants.

Power plant heat rate is usually corrected to reference conditions – commonly given by the OEM or by the EPC contractor – to validate the power plant efficiency parameters achieved are in line with the guaranteed performance of the plant.

A precise heat consumption measurement must be provided so that the calculated heat rate is as precise as possible. Depending of the type of power plant this could be a direct measurement, like in a combined cycle performance test an indirect measurement like in a coal power plant performance test.

In order to provide the highest engineering quality measurements TGPS performs overall plant efficiency test programs in accordance with the internationally recognized standards such as ASME PTC46.

The main thermal power generation cycle components will always require auxiliary equipment to operate efficiently and safely. TGPS can measure and analyze the auxiliary systems and identify troublesome equipment to ensure optimization of the plant net electrical output. This is a critical measurement to include as one of the power plant efficiency parameters to evaluate.

The auxiliary consumption represents a real challenge to improve sometimes, which has a direct impact in the power plant efficiency which is often overlooked.

Error in the measurement of auxiliary power consumption translates into error in the calculated net power output and thus must be minimized. TGPS can offer advice on what measures to take to improve auxiliary consumption and therefore the financial performance of power plants through net electrical output gains.

Every startup and shutdown means additional costs to power plant operators, it is one of the Power Plant Performance Efficiency Parameters that is used also by the dispatch to make decisions on which power plant to start-up or shutdown. It is important to understand the costs of these activities to optimize the management of the assets.

TGPS removes the assumptions out of these parameters by actually measuring the startup – shutdown cycle with actual monetary value that will be specific to each generation group. To estimate the actual costs of starting or shutting down a power plant, several other power plant efficiency parameters must me examined.

Considerations for estimating the costs is that these depend on the type of shutdowns: cold, warm, or hot. TGPS can help estimate specific costs taking into account critical power plant efficiency parameters such as the cost of startup fuel input and net electrical power used during start up & shut down of power plants.

The gas turbine compressor is a component that operates under heavy demand. If compressor efficiency is affected, it will consume more energy to compress the gas that is delivered to the turbine and the overall net power output and efficiency of the cycle decreases. The compressor is the first component of the cycle and therefore its effects will carry over to the rest of the cycle.

The turbine efficiency is defined as the ratio between the actual power produced in the turbine over the power that would be produced in an ideal turbine. A decrease in efficiency means that the overall net power output of the cycle decreases (and heat rate increases).

Including the turbine and compressor efficiency in the list of Power Plant Performance Parameters to evaluate should be a priority in any power generation project that uses gas turbines.

The “PTC22 – Performance Test Code on Gas Turbines” and ISO2314 – Gas Turbines Acceptance Tests are the relevant protocols used by TGPS to determine the performance of gas turbines.

Control systems need an accurate measurement of gas turbine exhaust to maintain a safe operation and to mitigate the possibilities of “overfiring” or “underfiring” in the combustion chamber. TGPS can provide high precision instrumentation to measure this parameter and reliable standards to calibrate site instrumentation. Both conditions affect the financial performance of power plants.

A higher exhaust temperature could be a symptom pointing to compressor or turbine inefficiencies. TGPS can perform a diagnostic analysis to identify underlying causes for an unexpected gas turbine exhaust temperature or flow variances.

Gas turbine exhaust flow characteristics have added importance when it is used as heat input to a steam cycle. The accurate measurement of mass flow and temperature are needed in order to estimate the performance of the HRSG and the steam cycle.

Using mobile high precision equipment TGPS can measure the levels of combustion products such as oxygen, carbon dioxide, carbon monoxide, nitrogen, sulfur dioxide, sulfur trioxitde, nitric oxide, nitrogen dioxide, hydrogen sulfide, and hydrocarbons. Testing is conducted in accordance with ASME PTC19.10 – Flue and Exhaust Gas Analyses and all EPA applicable protocols.

Noise emissions are accurately measured to ensure power plant noise emissions are compliant with local and contractual noise regulations. For most power plants, the major noise sources during operation are the air-cooled condenser or cooling tower (due to the fans), the gas and steam turbine, and the heat recovery steam generator (HRSG).

TGPS follows the guidelines set by ASME PTC36 – Measurement of Industrial Sound and ISO 10494 – Measurement of emitted Airborne noise for GT’s for the measurement of airborne sound emissions from stationary sound sources and facilities.

The HRSG is a vital component for any combined cycle power plant. The HRSG duty is critical power plant performance parameter to evaluate. It is the rate of heat transfer from the gas turbine exhaust gases to the water cycle. Optimizing HRSG duty means more energy is recouped and used in generating electricity and revenue.

The performance of the HRSG must be measured carefully so that the errors introduced into the calculation of the steam turbine performance is minimized. TGPS has over 20 years of experience in evaluating HRSG performance using as industry guideline ASME PTC 4.4 – Gas Turbine Heat Recovery Steam Generators.

The steam turbine is one of the most important components in the cycle. It transforms heat energy from the steam to mechanical energy for the generator. It is the element that most directly creates revenue for the plant. The heat rate and power output of the steam turbine can be corrected to reference conditions to compare the current performance of the turbine to rated performance. To validate the financial outlook of a plant it is essential for a steam turbine owner/operator to make sure that OEM guarantees are met at the time of delivery.

The steam turbine performance has a direct impact in several other Power Plant Performance Parameters around the plant.

TGPS conducts steam turbine performance testing per industry standard ASME PTC 6 – Steam Turbines code to determine these values.

The condenser represents the heat sink of the cycle. The performance of this very important has a significant impact on the overall cycle efficiency. Many times overlooked the condenser efficiency is one of the Power Plant Performance Parameters to include during the evaluation of the power plant. Even if it is outside of the boundary conditions, the condenser must be carefully examined as it can impact several other Power Plant Performance Parameters.

Condensers normally operate on a vacuum so that the pressure differential across the steam turbine is greater and thus more energy can be extracted from the steam, and so the condenser has a very important role in maximizing the efficiency of the cycle. Relevant power plant efficiency testing procedure is the ASME PTC 12.2 – Steam Surface Condensers.

The cooling tower is needed when a natural cooling source is not available. The plant rejected heat is treated through the condenser to the atmosphere and returned the cooling water to the condenser at the lowest possible temperature. The cooling tower efficiency is one of the Power Plant Efficiency parameters to include during each power plant performance evaluation.

A lower cooling-tower delivery temperature will produce a lower condenser pressure and therefore a greater steam turbine power output. The cooling tower is designed to deliver a rated cooling water outlet temperature at reference operating conditions. It is important to confirm this performance level through standardized performance tests.

TGPS conducts performance evaluations for mechanical and natural draft cooling towers, as well as other cooling systems such as closed circuit evaporative (wet) coolers, and wet surface air-cooled steam condensers in accordance with ASME PTC 23 – Atmospheric Water Cooling Equipment.