Regarding thermomechanical engines, the first law efficiency has been until now, the most used criterion, with the famous equilibrium thermodynamics upperbound given by the CARNOT formula. Most recently (second part of the past century), a new appraisal appears, regarding the maximum power objective for the engines. We propose here to reconsider these two main approaches due to the fact that the heat expanses first, and the heat rejected secondly are also involved in the complete characterization of the engine. These three quantities (energy consumption to minimize associated to the cost ; useful effect to maximize ; heat rejection to minimize, in order to protect the environment) are combined through a weighting procedure allowing, to discuss and choose the best scheme. Particular previous studies results are recovered and synthesized. Other new possibilities are proposed to be explored in the near future.

Harnessing biomass-derived energy can improve environmental and economic sustainability of a Combined Heat and Power production. The paper presents a new decision making policy and its application in meeting the energy up-grading needs of the Bari airport (300 kWe), based on an economic-environmental analysis related to the use of different bioenergy from short chain (<70 km). The main aim of this paper is to demonstrate how a "Zero Kilometer Energy" design model in a CHP plant represents a more sustainable alternative to the same conventional energy systems, regarding to the impact on the local socio-economic system. The study has been carried out in order to promote a synergistic and sustainable relationship between a territory and the infrastructures that service it, in terms of energy supply chain. For this purpose, three different bioenergy production systems (biomass from wood waste, vegetable oil / biodiesel and biogas from food waste) harnessing local agro-energy resources in Apulian region (Italy) were analyzed. The analysis has been integrated by a DCF (Discounted Cash Flow) Method, identifying the economic feasibility to make an informed choice. Finally the theoretical paybacks under different governmental incentive schemes, from 2012 to 2015, have been calculated along with estimated carbon savings to highlight the energy market trends for the different biomass resources.

Desiccant-based air handling units allow significant reductions in greenhouse gas emissions and energy savings with respect to conventional air conditioning systems. Benefits are maximized when they interact with renewable energy technologies, such as solar collectors. Due to the high requirements of humidifiers, water consumption is a major issue for desiccant cooling technology. Therefore, a water consumption analysis should be also performed.In this work, experimental tests and data derived from scientific and technical literature are used to implement a model of a solar desiccant cooling system, considering three different solar caption technologies (air, flat plate and evacuated collectors). Simulations were then performed to compare the energy, environmental and economic performance and water consumption of the system with those of a desiccant-based unit in which regeneration thermal energy is supplied by a natural gas boiler, and with a conventional air handling device. A trade-off solution is chosen, consisting of 16 m2 of flat-plate solar collectors. This solution allows to obtain, with respect to the reference system, a reduction of primary energy consumption and of the equivalent CO2 emissions of 24.2% and 27.1%, respectively, with an acceptable pay-back time of 4.81 years, and a water consumption very similar to that of the reference system.

Electric power shortfall in Pakistan is 2000MW in winter and it reaches 6000MW in summer season. Conventional energy sources are used to provide 80 % of Pakistan electric power. This paper gives the solution of shortfall by utilizing wind and biomass sources in Punjab province of Pakistan. The hybrid system of biomass and wind energy is modelled in this paper for the Punjab. The technical and economic analysis was presented for the rural areas. The animal manure was used as the feedstock of biomass. The biogas from the anaerobic digestion of the biomass was used to fulfil the energy needs. The wind potential location in Punjab was highlighted in this paper. The optimization of the model is performed irrespective of fossil fuels share. A sensitivity analysis of at least 27 % share from renewable sources is executed and the results are discussed. A comparative study of different RES hybrid systems is being discussed with respect to cost. It was found that the biomass wind hybrid system is the most comprehensive alternative to be adopted among other RE systems.

Cameroon is home to about 20 million inhabitants living on 475 440 km² land area located in central Africa. Since the years 2000, the country has been facing an unprecedented energy crisis. The energy demand had been growing while investments were still below acceptable level to provide energy to all sectors. Economic activities are negatively affected by the energy shortage - characterized by the rationing and frequent power cuts which seriously undermine factories’ operation. This situation has led to slow economic growth and increased price of commodities. To cover part of their electricity needs, industrial companies have acquired diesel engines which not only pollute but add to production costs. The paper examines Cameroon’s energy situation with focus on the industrial sector. The study concludes that Cameroon has a huge renewable energy potential. Alternative solutions are not implemented nor investigated by industrial companies who prefer to pass on the additional production costs to consumers. Sustainable solutions such as solar energy integration and energy generation from solid waste are suggested. But prior to the implementation, energy laws and regulations should be mastered by professionals and industries sensitized on the benefits of renewable energies and energy efficiency practices.

The New Zealand research station at Scott Base, Antarctica is used as a study of incorporation of wind power generation into an isolated microgrid powered by diesel generator. The generation plant at Scott Base uses waste heat from the generator to supply heating loads. The Antarctic conditions require gearless wind turbine generators, and the limitations on transport and construction vehicles as well as the demand levels lower than 200 kWe dictated the possible size of wind turbine. Energy audit data from the base was used to develop a load model. The current power and heat generation system was simulated using HOMER. The incorporation of wind turbines using local weather data was simulated and an optimal system design determined, based on measure of merit being total fuel consumption. Battery storage is costly, so a novel idea of demand side management was explored by effectively storing energy in the form of laundry when excess wind is available and curtailing laundry use when wind speeds are low. Simulations of this deferred load showed increased fuel savings could be gained through demand side participation.

Accurate forecasting of solar resource is the key issue for a successful integration of solar plants into the grid. This paper proposes a fuzzy logic approach as an alternative to classical statistics, aiming to forecast hourly global solar irradiation. Hourly clearness index is the quantity directly processed by the proposed fuzzy algorithms. Hourly clearness index is defined as the hourly horizontal global solar irradiation at the ground and the hourly solar irradiation at the top of the atmosphere. Clearness index takes into account all random meteorological influences, being a measure of the atmospheric transparency. Thus, the stochastic component of hourly solar irradiation can be isolated by means of the clearness index. Four new autoregressive-fuzzy models are studied in this paper. The models are mainly differentiated by the number of the input variables and the number of attributes. The model #1 has only one variable at the input (hourly clearness index measured at time t-1) which is characterized by 3 attributes. The model #2 extends the number of inputs increasing the order of auto-regressive terms to two. The model #3 adds to model #1 an exogenous input, namely relative sunshine. The model #4 includes a seasonality term. Overall results show that the model #4 performs the best. The novelties related to the fuzzy model assembly are the membership functions of the attributes and the simple matrix of fuzzy rules. In principle, the actual model can be applied in sites where measurement of hourly global solar irradiation is currently performed, only a re-estimation of the parameters being necessary. The results demonstrate that the fuzzy models have the strength to translate the information enclosed in past measurements into an actual prediction with acceptable accuracy.

This paper conducts an analysis study on effect of the heat source flowrate on heat transfer characteristics of a preheater and system performance of a 250-kW level organic Rankine cycle (ORC) system. Refrigerant R245fa is used as working fluid with a constant flowrate of 11.58 kg/s. The operating pressures of the preheater/evaporator and the condenser are 1.265 MPa (i.e., evaporation temperature, T_R,eva, of 100 ^oC) and 0.242 MPa (i.e., condensation temperature of 39 ^oC), respectively. The analyzed heat source flowrate (m_w) is ranging from 9.39 kg/s to 27.39 kg/s with a constant inlet temperature of 133.9 ^oC. The efficiencies of the used pump, turbine, and generator are set to 90%, 80%, and 90%, respectively. The net power output is 243 kW and the system thermal efficiency is 9.46% under design conditions (m_w = 15.39 kg/s). For an off-design heat source flowrate, a new operating pressure of the preheater/evaporator will be chosen to meet that R245fa reaches the saturation liquid state at the outlet of the preheater and the saturation vapor state at the outlet of the evaporator, i.e., without superheating. The results demonstrate that (1) the operating pressure of the preheater/evaporator increases from 0.775 MPa to 1.675 MPa (i.e., T_R,eva increases from 79.3 ^oC to 113.2 ^oC) with an increase in m_w, ranging from 9.39 kg/s to 27.39 kg/s; (2) the higher m_w presents the better heat transfer performance of the preheater and the smaller requirement of heat capacity of the evaporator; and (3) the net power output (172 kW to 282 kW) and the system thermal efficiency (7.07% to 10.65%) increase with an increase in m_w, especially for m_w < 17.39 kg/s.

We show that the measurement of the power curve of a small-scale wind turbine system following the IEC 61400-12-1 standard might lack consistency. This is due to characteristics specific to small-scale wind turbines and data processing. We give recommendations to ensure consistency, accuracy and reproducibility of the measurements. Besides, in the hope of making the standard more accessible, we clarify the importance of various test parameters such as anemometer position, battery voltage, and controller settings. Our Matlab code used for data processing is included.

Power converter is one of the essential elements for effective utilization of renewable power sources. This paper focuses on the development of a circuit simulation model for solar power maximum power point tracking (MPPT) evaluation with different buck-boost converter topologies including SEPIC, ZETA, and four-switch type buck-boost DC/DC converters. The circuit simulation model mainly includes three subsystems, namely, a PV emulator model, a buck-boost converter based MPPT system, and a fuzzy logic MPPT controller. A buck-boost converter based dual regulation (voltage regulation and current regulation) modes PV emulator is built to emulate the characteristics of the PV panel. The PV emulator is used to power the MPPT system. The MPPT system also contains a buck-boost power converter for power transfer. The maximum power point tracking function is achieved through proper control of the power switches of the power converter. A fuzzy logic controller is then developed to perform the MPPT function for obtaining maximum power from the PV panel. The MATLAB based Simulink piecewise linear electric circuit simulation tool is used to verify the complete circuit simulation model.