Rankine Cycle efficiency gain using thermoelectric heat pumps

The Rankine cycle remains the dominant method of thermal plant electricity generation in the world today. The cycle was described over 150 years ago and significant performance advances continue to be realised. On-going metallurgy research has enabled the operating pressure and temperature of the boiler and turbine to be increased, thereby improving the cycle efficiency. The ubiquitous use of the Rankine cycle on a massive scale in conjunction with fossil fuels as the energy source continues to motivate further efficiency improvements in the cycle.<p></p> Previous work established a theoretical basis for the use of thermoelectric heat pumps (THPs) in the condensation process of the Rankine cycle to positively impact cycle efficiency. The work presented here experimentally validates this prior work and provides performance metrics for current commercially available THPs and quantifies how their use can increase the efficiency of the Rankine cycle as implemented in a large power plant.<p></p> A commercial THP is characterised to obtain its Coefficient of Performance (COP) variation with input current and the amount of thermal energy transported. A larger-scale system comprising of a multistage thermoelectric heat pump is then considered, demonstrating that using commonly available THPs a fuel load reduction of over 1.5% is achievable for a typical generating set whilst simultaneously increasing the overall plant cycle efficiency from 44.9% to 45.05%.<p></p> The paper concludes with a cost-benefit analysis of the system, showing that over a four year period the saving in fuel used can easily re-coup the capital cost incurred by the addition of the condenser heat pump

Combined heat and power system for stoves with thermoelectric generators

Solid-fuel stoves are used in developing countries, remote locations, and in general more commonly due to convenient fuel cost for space heating. The possibility of also using the stove heat to heat water and produce electricity represents an added benefit. This work presents an application of thermoelectric generators to a solid-fuel stove to concurrently charge a lead-acid battery and transfer heat to water for heating or household use. The feasibility of the proposed CHP system is demonstrated for a common solid-fuel stove. This system produces an average of 600 Wth and 27 Wel (42 Wel peak) during a 2-h long experiment in which the TEG efficiency is around 5% and the MPPT efficiency of the power converters used is demonstrated

Thermoelectric energy harvester with a cold start of 0.6 °C

This paper presents the electrical and thermal design of a thermoelectric energy harvester power system and its characterisation. The energy harvester is powered by a single Thermoelectric Generator (TEG) of 449 couples connected via a power conditioning circuit to an embedded processor. The aim of the work presented in this paper is to experimentally confirm the lowest ΔT measured across the TEG (ΔTTEG) at which the embedded processor operates to allow for wireless communication. The results show that when a temperature difference of 0.6 °CΔTTEG is applied across the thermoelectric module, an input voltage of 23 mV is generated which is sufficient to activate the energy harvester in approximately 3 minutes. An experimental setup able to accurately maintain and measure very low temperatures is described and the electrical power generated by the TEG at these temperatures is also described. It was found that the energy harvester power system can deliver up to 30 mA of current at 2.2 V in 3ms pulses for over a second. This is sufficient for wireless broadcast, communication and powering of other sensor devices. The successful operation of the wireless harvester at such low temperature gradients offers many new application areas for the system, including those powered by environmental sources and body heat

Rotating filters permit wide range of optical pyrometry

Gear-driven dual filter disks of graduated density vary linearly with respect to rotation, allowing a wide range of photographic pyrometry. this technique is applicable in metallurgy, glass, plastics and refractory research, and crystallography

A theoretical/experimental program to develop active optical pollution sensors: Quantitative remote Raman lidar measurements of pollutants from stationary sources

Typical pollutant gas concentrations at the stack exits of stationary sources can be estimated to be about 500 ppm under the present emission standards. Raman lidar has a number of advantages which makes it a valuable tool for remote measurements of these stack emissions. Tests of the Langley Research Center Raman lidar at a calibration tank indicate that night measurements of SO2 concentrations and stack opacity are possible. Accuracies of 10 percent are shown to be achievable from a distance of 300 m within 30 min integration times for 500 ppm SO2 at the stack exits. All possible interferences were examined quantitatively (except for the fluorescence of aerosols in actual stack emissions) and found to have negligible effect on the measurements. An early test at an instrumented stack is strongly recommended

Micrometeoroid penetration measuring device Patent

Measuring micrometeroid depth of penetration into various material

A three-point-based electrical model and its application in a photovoltaic thermal hybrid roof-top system with crossed compound parabolic concentrator

A new coupled optical, thermal and electrical model is presented in this study and applied to a 27 concentrating photovoltaic thermal (PV/T) system for predicting the system performance under 28 various operational conditions. Firstly, a three-point-based electrical model and a method for 29 extracting its five model parameters are developed by using the currents and voltages at the short-, 30 open-circuit and maximum power points provided in usual PV module/panel datasheets. Then, the 31 model and method are validated with the existing six flat-plate PV modules and subsequently are used 32 to predict the hourly electrical performance of the CPV/T roof-top system designed by us under 33 outdoor conditions on four clear days by integrating with a scaling law developed by us. Additionally, 34 transient effect and water temperature on the storage tank are examined. It turned out that the CPV 35 system could operate for 6 hours a day with a peak instant electrical power of 50W/m2 and could 36 generate 0.22kWh/m2 electricity a day in May-July. The error in hourly electrical energy gained 37 between the predictions and observations is in a range of (3.64-8.95)% with the mean of 5.53 % in 38 four days, and the estimated water temperature in the storage tank agrees with the monitored one in 39 range of 0.2-1oC. The proposed methods as well as the electrical models could potentially be applied 40 widely across the solar energy field for the management and operation of the electrical energy 41 production from any CPV/T roof-top system

Thermal performance of two heat exchangers for thermoelectric generators

Thermal performance of heat exchanger is important for potential application in integrated solar cell/module and thermoelectric generator (TEG) system. Usually, thermal performance of a heat exchanger for TEGs is analysed by using a 1D heat conduction theory which ignores the detailed phenomena associated with thermo-hydraulics. In this paper, thermal and mass transports in two different exchangers are simulated by means of a steady-state, 3D turbulent flow k -e model with a heat conduction module under various flow rates. In order to simulate an actual working situation of the heat exchangers, hot block with an electric heater is included in the model. TEG model is simplified by using a 1D heat conduction theory, so its thermal performance is equivalent to a real TEG. Natural convection effect on the outside surfaces of the computational model is considered. Computational models and methods used are validated under transient thermal and electrical experimental conditions of a TEG. It is turned out that the two heat exchangers designed have a better thermal performance compared with an existing heat exchanger for TEGs, and more importantly, the fin heat exchanger is more compact and has nearly half temperature rise compared with the tube heat exchanger

Indoor characterization of a reflective type 3D LCPV system

This is the final version of the article. Available from AIP Publishing via the DOI in this record.Low concentrating photovoltaic (LCPV) systems produces higher electrical output per unit solar cell compared to typical PV systems. The high efficiency Si solar cells can be utilized with little design and manufacturing changes for these applications. However, a key barrier towards achieving economic viability and the widespread adoption of LCPV technologies is the losses related to high operating temperature. In the present study, we evaluate the performance 3D low concentration system designed for 3.6x, using a reflective Cross compound parabolic concentrator (CCPC) and a Laser Grooved Buried Contact solar cell having an area of 50∗50mm 2 . Results demonstrate the losses occurring due to the temperature rise of the solar cell under concentration and we analyze the potential which could be utilized for low grade heating applications.The authors gratefully acknowledge financial support received from the EPSRC through Solar Challenge project SUNTRAP (EP/K022156/1). We would also like to thank the Super Solar Hub for providing us with the travel grant for this conference

Multiphysics simulations of thermoelectric generator modules with cold and hot blocks and effects of some factors

This is the final version of the article. Available from Elsevier via the DOI in this record.Transient and steady-state multiphysics numerical simulations are performed to investigate the thermal and electrical performances of a thermoelectric generator (TEG) module placed between hot and cold blocks. Effects of heat radiation, leg length and Seebeck coefficient on the TEG thermal and electrical performances are identified. A new correlation for the Seebeck coefficient with temperature is proposed. Radiation effects on the thermal and electric performances are found to be negligible under both transient and steady-state conditions. The leg length of the TEG module shows a considerable influence on the electrical performance but little on the thermal performance under transient conditions. A nearly linear temperature profile on a leg of the TEG module is identified. The temperature profile of the substrate surfaces is non-uniform, especially in the contacted areas between the straps (tabs) and the substrates.The work is supported by EPSRC SUPERGEN Solar Challenge with grant: EP/K022156/1-Scalable Solar Thermoelectrics and Photovoltaics (SUNTRAP)