Total Annual Energy Consumption Research Articles

Multiobjective Optimal Unit Sizing of a Grid-Connected Photovoltaic System in Consideration of its Probabilistic Characteristics.

A probabilistic approach to the optimal unit sizing of a grid-connected photovoltaic system without storage battery is presented. The surface area of the photovoltaic array, the capacity of the receiving device, and the electric contract demand are determined so as to minimize the expected values of the annual total cost and annual energy consumption subject to the loss of power supply probability, in consideration of probabilistic characteristics of solar insolation and electricity demand. This optimization problem is considered as a multiobjective one, and a discrete set of Pareto optimal solutions is derived numerically by using the weighting method. A case study on a system with the option of reverse power flow into the grid is carried out using measured data on solar insolation. The trade-off relationship between the two objectives is clarified and optimal values of the above design items are determined in relation to the loss of power supply probability. The results obtained by this probabilistic approach are compared with those for the deterministic approach.

Multiobjective Optimal Unit Sizing of Hybrid Power Generation Systems Utilizing Photovoltaic and Wind Energy

A deterministic approach to optimal unit sizing is presented for hybrid power generation systems utilizing photovoltaic and wind energy. Device capacities and electric contract demand are determined so as to minimize the annual total cost and annual energy consumption from the viewpoints of economy and energy saving or reduction in NOx and CO2 emission, respectively. This optimization problem is considered as a multiobjective one, and a discrete set of Pareto optimal solutions is derived numerically by using the weighting method. Two systems interconnected with the electric power grid are investigated: one has the option of reverse electricity flow into the grid, and the other has no option. By carrying out some case studies, the tradeoff relationships between the two objectives as well as the optimal values of device capacities are clarified. The influence of electricity deficit on unit sizing is also investigated.

Energy consumption and the potential for energy conservation in school buildings in Hellas

School buildings (238) in Hellas were audited for construction, heating, cooling, lighting, and mechanical and electrical systems. The annual average total energy consumption is 93 kWh/m 2, of which approximately 72% is consumed for space heating. The assessment of various energy-conservation techniques shows a potential for 20% overall energy conservation.

Energy performance and energy conservation in health care buildings in hellas

Energy performance data for 30 health care buildings have been collected during an extensive energy audit of buildings in Hellas, within the frame of a National Energy Programme sponsored by the CEC VALOREN Programme for energy conservation in buildings. This short monitoring campaign was performed with on-site visits of a trained panel of engineers to each building, in order to register all information relevant to the buildings' construction, heating, cooling, lighting, systems and all other mechanical and electrical systems. The technical results of these audits, the role of the cooling and heating systems on the energy consumed in health care buildings, are discussed. The annual average total energy consumption in hospitals is 407 kWh/m 2 and in clinics is 275 kWh/m 2, the majority of which is consumed for space heating (73.4% in hospitals and 65.3% in clinics). Several scenarios for possible interventions to the outer envelope of the buildings and to the heating, cooling and lighting systems, are proposed and evaluated, in order to assess the effectiveness of various energy conservation techniques. Based on the results from several simulations, it is concluded that it is possible to reach an overall 20% energy conservation. The energy consumption for heating can be reduced by 15% in hospitals and 11% in clinics by using more efficient heat production and distribution systems. Proper insulation of the buildings can conserve 173 kWh/m 2 in hospitals and 103 kWh/m 2 in clinics. Cooling can be reduced by 68% (in hospitals) and 56% (in clinics) by using night ventilation and by 80 and 97%, respectively, by using ceiling fans. Natural cooling techniques, under certain conditions, can also provide an important reduction of the cooling load. The use of high efficacy lamps can reduce the electric energy consumed for lighting by up to 50%. This information provides a representative picture of the existing conditions on energy consumption in health care buildings and can be used as guidelines for future energy efficient building construction.

Multiobjective Optimal Unit Sizing of Hybrid Power Generation Systems Utilizing Photovoltaic and Wind Energy.

An optimal unit sizing method is developed for hybrid power generation systems utilizing photovoltaic and wind energy. Equipment capacities and electric maximum demand are determined so as to minimize the annual total cost and annual energy consumption from the viewpoints of economy and energy conservation, respectively. This optimization problem is considered as a multiobjective one, and a discrete set of Pareto optimal solutions is derived numerically using the weighting method. Two systems interconnected with the electric power grid are inventigated : one has the option of reverse power flow into the grid, and the other, no option. By carrying out some case studies, the trade-off relationships between the two objectives are clarified, and optimal values of equipment capacities are determined. The effect of electricity deficit on unit sizing is also investigated.

Estimate of agro-industrial wastes: A case study for Thailand

Annual production of rice husk in Thailand is estimated to be 5·08 M tons out of which 3·81 M tons could be available as surplus after meeting all energy requirements of the rice mills. Total annual production of bagasse is 7·13 M tons out of which 1·35 M tons could be available as surplus. The total annual sawdust production is about 0·106 M tons. Energy equivalents of surplus rice husk, surplus bagasse and sawdust production are 6·2, 1·6 and 0·22% of Thailand's total annual energy consumption respectively.

Impact of electric lighting efficiency on the energy saving potential of daylighting from roof monitors

A developmental version of the building energy analysis computer program BLAST was used to perform simulations of a prototypical, single-story office building. Total annual energy consumption was computed using Typical Meteorological Year (TMY) [1] weather data from three locations in the United States. For each location, two electric lighting designs were tested on the baseline building (no roof monitors) to compare the energy requirements of current-practice and more efficient electric lighting designs. Then roof monitors were added to evaluate their energy saving potential for each of the electric lighting designs. The roof monitors had highly diffusing, vertical glazings facing southeast and southwest. The results show that improving electric lighting system efficiency and adding roof monitors for daylighting both have the potential for substantially reducing lighting electricity and the energy cost of operating the building. The potential benefits of daylighting are substantially lower for a building outfitted with a more efficient electric lighting system, although still significant. To determine the limits of validity of the simulations, a number of sensitives studies were performed. Among the issues investigated were: dirt deposits, snow accumulation, glazing optical properties, interior design, luminous efficacy of admitted sunlight, and thermostatic controls.

Saving energy in health buildings

There are over 2, 000 hospitals in England and Wales. Fuel costs account for almost 70 per cent of the energy operating costs. The remainder covers items such as salaries of operating staff, maintenance, electricity and water. £192 million was spent on fuel in 1979–80. For this period the total annual energy consumption was 78 million GJ for the hospital estate in England and Wales which has a volume of about 83 million m3. With such a large variety of hospital buildings and uses there are inevitably large variations in energy consumption across the country. A decision model has been formulated which will coordinate the decisions made on energy conservation throughout the hospital estate.

Bird community energetics in a boreal coniferous forest

The annual minimum energy consumption of the bird community was 2524 × 103 kcal km−2, of which 44% was consumed by wintering species and 73% by passerines. The daily energy consumption was in summer 14–16 × 103 and in winter 1–2 × 103 kcal km−2. In spruce forests and in afforested swamps birds required approximately 0.12% of the net primary production. Their total annual energy consumption was covered by invertebrates (59%), vertebrates (2%) and vegetable matter (39%); the food derived from the ground (55%), from trees (44%) and from the air (1%). Arboreal insectivorous passerines, ground passerines and gallinaceous birds were the most important ecological guilds. Among passerines existence metabolism accounted for 73% of the annual energy consumption, extra activity for 17%, breeding activity for 1%, moult for 4% and nestlings for 4%.

Energy utilisation in the glasshouse industry

AbstractThe total annual energy consumption in Britain is about 9505×109 MJ of which agriculture directly uses less than 1.4% to produce over 50% of the country's food. Of the agricultural consumption, glasshouse heating uses 35%, or 900 000 tonnes, of fossil fuel annually. Heating costs account for about 30% of production costs of glasshouse crops. Boilers used on glasshouse holdings can operate at thermal efficiencies of 80–85% with an overall system efficiency of at least 70%. Ways of increasing efficiency are discussed.Heat losses from glasshouses are high compared with other buildings due to the light‐transmitting envelope but can be reduced by good maintenance, provision of windbreaks and the use of insulating covers drawn over the crop at night. Double skinning by lining with clear plastic film offers attractive fuel savings but the consequential light loss and crop reduction is likely to result in a net monetary loss. Research on crop response to temperature has established optimum temperature regimes for most crops. Reduction of temperature to save fuel usually results in a loss of crop and income which greatly exceeds the fuel saving. The use of light modulated temperature controllers offers promise of increasing the output from a given fuel input. The use of waste heat from electricity generation and industrial processes is unlikely to give any benefit in the near future.