Novel System for Distributed Energy Generation from a Small Scale Concentrated Solar Power

Abstract

The present work describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings.The developed system integrates small-scale concentrator optics with moving and tracking components, solar absorbers in the form of evacuated tube collectors, a heat transfer fluid, a Stirling engine with generator, and heating and/or cooling systems; it incorporates them into buildings in an architecturally acceptable manner, with low visual impact. Some good results have already been achieved, while developments on several technology subcomponents will be finalized through first part of 2013.Two Cer.Met. have been modelled, realized and tested. The up scaled receiver, in form of Cer.Met. coating based on TiO2 -Nb, has been confirmed an absorptance of 0.94 and emittance of 0.1 (@350°C). A second Cer.Met. coating based on SiO2 -W has demonstrated an absorptance of 0.93 and emittance of 448 Luigi Crema et al. / Energy Procedia 57 ( 2014 ) 447 -456 0.09 (@350°C). A full-evacuated solar tube has been designed and realized, with absorber of 12 mm in diameter and length in 2 meters.The system is provided of a concentration ratio 12:1, and a single module is 200 cm long, 40 cm wide and 20-25 cm high. Two or more modules can be combined. The evacuated solar tube, located on the focus, has the selective absorber on a tube of 12 mm in diameter. A very thin glass mirror has been developed (< 1 mm). The overall mirror reflectivity has been measured, the verified value is 0,954.Research has proposed a high energy density, double acting Stirling engine, provided of innovative heat exchangers realized through Selective Laser Melting process. The engine is a low speed (250 RPM), high pressure (130 Bars) and compact solution able to be run at 300°C and generate 3,5 kW nominal power.The solar technology has actually entered the proof-of-concept stage. A solar plant has been installed in Malta, by Arrow Pharm company, supplying the industrial process of generated steam at 180°C and 3.5 absolute pressure. The solar collector's efficiency is close to 47% in presence of 900 W/m2 of direct solar radiation.During 2013, solar evacuated tubes with innovative Cer.Met. coating, together with new thin glass mirrors will upgrade the demonstration site, together with a new and innovative low temperature difference and high energy density Stirling. By end-2013, the system will be demonstrated, with the overall objective to achieve a minimum of 65% in solar collectors' efficiency at 300°C, and 12 -15% of overall electrical efficiency by the Stirling cycle.The actual work is part of a FP7 European Funded project, DIGESPO [1].

A review of solar energy based heat and power generation systems

“…Concentrating thermal collectors based systems. Crema et al [60][61][62] presented the numerical and experimental study of a modular mCHP plant producing 1-3 kW electrical power and 3-9 kW thermal power using parabolic trough collectors with evacuated tube receivers and a Stirling engine. The plant was designed to provide electricity, heating, and cooling to single and multiple dwellings and other small buildings.…”

Solar collectors and photovoltaics as combined heat and power systems: A critical review

“…Also, many types of research have been done for developing the model of small-scale solar thermal trigeneration plants consisting parabolic trough collectors and ORC units [93][94][95][96][97][98]. In 2014, a concentrated solar combined heat and power plant scheme was presented by Han et al [21].…”

“…The output of this article demonstrated that the performance of the expander isentropic was satisfactory, and it could be enhanced by changing some mechanical parts. The total produced energy of the proposed configuration was 1710 kWh.Crema et al[94] assessed the integration of evacuated tubes to a micro-CHP configuration, composed of CSP and Stirling engine system, in building sector. The proposed combination was satisfying in supplying the demands of the buildings.…”

Laser Profilometry on Micro-PTC

“…For the production of heat at a medium temperature, 150-250 • C, solar collectors could be smaller with respect to the usual PTCs employed in the large high-temperature plants [1][2][3][4]. The advantage of having reduced dimensions permits to install these solar collection systems in small areas or even on building roofs [5][6][7][8]. The examined micro-PTC (m-PTC) is ten times smaller than a common PTC.…”