Primary Energy Utilization Research Articles

Time-dependent optimization of a large size hydrogen generation plant using “spilled” water at Itaipu 14 GW hydraulic plant

In this paper hydrogen generation and storage systems optimization, related to a very large size hydraulic plant (Itaipu, 14GW) in South America, is investigated using an original multilevel thermo-economic optimization approach developed by the Authors. Hydrogen is produced by water electrolysis employing time-dependent hydraulic energy related to the water which is not normally used by the plant, named “spilled water”.From a thermo-economic point of view, the two main aspects of the study are the optimal definition of the plant size and the whole system management. Both of them are strongly influenced by (i) spilled water energy variability related to its time-dependent distribution during the whole year, (ii) time-dependent electricity demand of Paraguay and Brazil (the owners of the Itaipu plant) electrical grids, and (iii) the hydrogen demand profile.The system analyzed here consists of a very large size hydrogen generation plant (hundreds of MW) based on pressurised water electrolysers fed with the so called “spilled water electricity”, the related H2 storage, and the H2 demand profile for Paraguay transport sector utilization.Since H2 plant optimal size is strongly correlated to optimal management and vice-versa, in this paper two hierarchical levels have been considered hour by hour on a complete year time period, in order to minimize capital and variable costs. This time period analysis is necessary to properly take into account spilled energy variability to find out H2 production system optimal size, optimal storage solution and best economical results.For the optimal storage size, two different solutions have been carefully investigated: (i) classical long time H2 physical storage using pressurised tanks at 200 bar; (ii) hybrid one using reduced size physical storage (one day time demand) where the energy to feed electrolysers is taken from electrical grid when spilled water energy is not available [Rivarolo M, Bogarin J, Magistri L, Massardo AF. Hydrogen generation with large size renewable plants: the Itaipu 14 GW hydraulic plant case. In: 3rd international conference of applied energy (ICAE), 16–18 May 2011, Perugia; 2011.]. For both the two solutions, time-dependent results are presented and discussed with particular emphasis to economic aspects, system size, capital costs and related investments. It is worthy to note that the results reported here for this particular H2 large size plant case represent a general methodology, since it is applicable to different size, primary renewable energy, plant location, and different H2 utilization.

Feasibility Study on Combined Heat and Power with Different Distributed Generation Technologies for Various Commercial Buildings

This paper has examined the energy consumption characteristics for six different buildings including apartments, offices, commercial buildings, hospitals, hotels and educational facilities. Then 50000m2 development site for respective building’s type has been assumed as case study to evaluate the introduction effect of Combined Heat and Power (CHP). All kinds of CHP systems with different distributed generation technologies including Gas Turbine (GT), Gas Engine (GE), Diesel Engine (DE), Solid Oxide Fuel Cell (SOFC) and Polymer Electrolyte Fuel Cell (PEFC), have been simulated by using HEATMAP, CHP system analysis software. And their primary energy utilization efficiency, energy saving ratio and CO2 reduction ratio have evaluated and compared respectively. The results can be summarized as follows: various buildings have their special heat to power ratio characteristics. Matching the heat to power ratio demanded from an individual building with that supplied from a CHP system is very important. It is necessary to select a reasonable distributed generation technologies according to the load characteristics of various buildings. Distributed generation technologies with high energy generating efficiency and low heat to power ratio, like SOFC and PEFC is more reasonable selection for Building Combined Heat and Power (BCHP). CHP system is an attractive option for hotels, hospitals and apartments. The users can achieve high energy saving and environmental benefit by introducing a CHP systems. In others buildings, especially like commercial buildings and offices, the introduction of CHP system is unreasonable.

China’s carbon emissions from urban and rural households during 1992–2007

In China, Rapid economic growth has stimulated fast urban expansion and rural household income and consumption expenditure. In current paper, an input–output method is used to determine the impact of China’s increased urban and rural household consumption on carbon emissions. The results shows that the direct and indirect CO 2 emission from household consumption accounted for more than 40% of total carbon emissions from primary energy utilization in China in 1992–2007. The population increase, expansion of urbanization and the increase of household consumption per capita all contribute to an increase of indirect carbon emissions, while carbon intensity decline mitigates the growth of carbon emissions. Therefore, at the domestic level, household consumption is of great significance for CO 2 emission, which could be mitigated through changing the composition of goods and services consumed by households, and switching to consumption pattern of less carbon-intensive products. The government must consider the substantial contribution of household consumption to carbon emissions when China is encouraging consumption in order to address the current global financial crisis.

Investigation and Evaluation on District Energy System at Kitakyushu Science and Research Park

A district energy system in Kitakyushu Science and Research Park (KSRP) has been introduced. In this paper, the system′s running situation was analyzed by using the recorded data in 2002. Generating electricity, heat recovery efficiency and recovery heat utilization efficiency for gas engine and fuel cell were calculated. On the basis of the above study, energy saving and CO2 reduction were evaluated.The results can be summarized as follows: 1) The on-site generating electricity equipments provided 51.2% of the total electricity demand, including fuel cell with 34.5%, gas engine with 13.4% and PV system with 3.3%. In total heat energy demand, 70% of hot water load, 30.9% of cooling load and 14.3% of heating load were provided by recovering the heat energy from fuel cell and gas engine system. 2) Fuel cell was running 8572 hours with constant generating electricity efficiencies, about 30.8%. Gas engine only run 4281 hours with higher generating electricity efficiencies, about 24.5%. PV system achieved over 8% module conversion efficiencies in 83% of generating electricity time. 3) Fuel cell had lower heat recovery efficiency, but this heat energy recovered almost was utilized by the heat exchanger or absorption chiller. Gas engine had higher heat recovery efficiency, but only 70% of them were utilized by heat recovery equipments. 4) Compared with the conventional energy supply system, the district energy system achieved 56% primary energy utilization efficiency, 10.9% saving energy ratio and 1.32% CO2 reduction ratio.

Highly efficient conversion technologies for energy utilization

Energy utilization systems and the related conversion technologies are evaluated from the thermodynamic view point in order to regulate the energy flow path. Involvement of thermal energy, directly as well as indirectly in any conversion process or operation is discussed, indicating that an innovative advancement of conversion technologies between heat and other forms of energy may be a breakthrough for ultimate energy utilization. Such highly efficient conversion technologies for the respective steps along the energy flow path, namely primary energy conversion, energy transportation and energy utilization including storage and recovery, are discussed.

The role of IGCC in CO2 abatement

Abstract IGCC technology per se involves the potential of highest efficiencies, thus reducing the CO 2 output accordingly. Moreover, the intermediate stage of synthesis gas makes it possible to remove most of the carbon compounds before combustion with acceptable additional auxiliary power demand. The separated CO 2 stream is of highest purity and therefore suited for disposal e.g. in the deep sea or for reuse in chemical syntheses. So, methanol synthesis based on power plant CO 2 has been investigated. This contribution presents the results of a pre-basic design for a coal-fired 300 MW-class IGCC power plant with methanol production using an external H 2 source. Based on a Siemens Model V94.3A gas turbine-generator, the standard IGCC has been equipped with plant components including CO shift reactors, CO 2 scrubber, methanol synthesis reactors and distillation unit; additional investment costs amount to approx. 25 %. This concept is based solely on proven process engineering methods. Primary energy utilization as well as the resulting methanol production costs based on appropriate generating costs are discussed. Comparative CO 2 emission figures make the advantage of such a coproduction process regarding this perfectly clear.

The hydrogen/hydride energy concept

With technology at its present stage, hydrogen is a very convenient secondary energy source (fuel, propellant) at the end of the oil era, as hydrogen (given the necessary primary energy, e.g. coal, nuclear energy for hydrogen production) is available in water in practically inexhaustible quantities and its distribution in the form of pure hydrogen or part-hydrogen gas mixtures (town gas) presents no fundamental technical problems. Hydrogen technology brought about as a result of the dwindling reserves of mineral oil offers particularly favourable advantages in that hydrogen, like oil, can be applied universally as an energy source not only for domestic and industrial use, but also for motor vehicles. The storage of hydrogen for mobile (vehicle) and stationary (domestic) applications is best undertaken by the aid of suitable metal hydrides. Hydride research at Daimler-Benz not only produced the world's first combination hydride vehicles, it also led to the discovery and further development of a series of possible applications for hydrides. This work shows, that hydrogen out of metal hydrides is not only environmentally acceptable and offers independence of petroleum supplies, metal hydrides also permit optimum primary energy utilization by means of waste heat recovery from all combustion processes, heating and cooling of houses and cars without consuming primary energy and a reduction in energy consumption during the production of inexpensive D 2O for natural uranium reactors.