Building Heat Demand Research Articles

Optimization of an SOFC-based decentralized polygeneration system for providing energy services in an office-building in Tōkyō

Decentralized energy systems are thought to have great potential for supplying electricity, cooling and heating demands of buildings. A decentralized system combining a solid oxide fuel cell (SOFC) with two absorption-chillers and a heat-exchanger is proposed. In order to minimize the CO 2-emissions and to compute the associated costs, a two-level optimization is performed. On the first level the design parameters of the system are optimized using an evolutionary algorithm, and on the second level the optimal daily operation of the system is optimized using a linear programming algorithm. The results are compared with the CO 2-emissions and costs of a typical conventional system that obtains the base electricity requirements as well as electricity for an electric chiller/heater system from the central power grid. The fully decentralized SOFC-based energy system could result in a potential CO 2 reduction of 45% at an estimated cost increase of about 290% compared to the conventional system.

Sanitary hot water consumption patterns in commercial and industrial sectors in South Africa: Impact on heating system design

A large amount of individual sanitary hot water consumers are present in the South African residential sector. This led to several studies being done on hot water consumption patterns in this sector. Large amounts of sanitary hot water are also consumed in the commercial sector in buildings such as hotels and in large residences such as those found in the mining industry. The daily profiles of sanitary hot water consumption are not related to any technical process but rather to human behavior and varying ambient conditions. The consumption of sanitary hot water, therefore, represents a challenge to the electrical utility because it is an energy demand that remains one of the biggest contributors to the undesirable high morning and afternoon peaks imposed on the national electricity supply grid. It also represents a challenge to sanitary hot water system designers because the amount of hot water as well as the daily profile in which it is consumed impacts significantly on system design. This paper deals with hot water consumption in the commercial and industrial sectors. In the commercial sector, we look at hotels and in the industrial sector at large mining residences. Both of them are served by centralized hot water systems. Measured results from the systems are compared to data obtained from previous publications. A comparison is also made to illustrate the impact that these differences will have on sanitary hot water system design. Simulations are conducted for these systems using a simulation program developed in previous studies. The results clearly show significant differences in the required heating and storage capacity for the new profiles. A twin peak profile obtained from previous studies in the residential sector was used up to now in studies of heating demand and system design in commercial buildings. The results shown here illustrate the sanitary hot water consumption profile differs significantly from the twin peaks profile with a very high morning peak in hot water consumption. This leads to a requirement for bigger heating and storage capacities in commercial buildings like hotels. A summary of the results are provided in the form of minimum design parameters for different hot water consumption profiles. This study emphasizes the importance of understanding the trends of hot water consumption in buildings, especially when demand side management projects are done on these types of systems.

CEPHEUS results: measurements and occupants’ satisfaction provide evidence for Passive Houses being an option for sustainable building

Passive houses offer extended living comfort with only 15–20% of the space heating demand of conventional new buildings while the extra costs of this standard are only about 10% of the total building costs. In the first part of this paper, detailed measurements for 11 “Passive House” projects with more than 100 dwelling units from the EU-funded demonstration project CEPHEUS (Cost Efficient Passive Houses as EUropean Standards) are presented. All projects exhibit extraordinarily low space heat consumptions. Compared with ordinary, newly erected buildings, 80% of the space heat consumption could be saved. The total primary energy consumption (including household electricity) was less than 50% of that of conventional new buildings. The measurements show that the buildings also offer comfortable indoor conditions in both summer and winter. Several social research studies revealed that the users are well pleased with their homes. The second part of the paper focuses on low-income tenant's satisfaction in the world's first multi-story Passive Houses in Kassel, Germany. This building contrasts sharply with the “standard” Passive House, occupied by its owners. A 2.5 year study was conducted from spring of 2000 to autumn of 2002. The development of opinions, attitudes, behaviour, and satisfaction over time could be recorded. The building is a clear success, the tenant's satisfaction is high. It is concluded that this building type fulfils the conditions of sustainability in social, ecological and economic respects and should therefore be disseminated on a larger scale. To this end, the last part of the paper describes the development of the Passive House standard in Germany, Austria and Switzerland, from the first demonstration project in 1991 to about 3500 dwelling units today. The prerequisites for this development are analysed. Finally, the authors give their view about the political possibilities for pushing Passive Houses into the market as well as for stimulating a market pull for this comfortable and energy efficient building type.

CORRECTION OF A DESIGNED BUILDING'S HEAT BALANCE ACCORDING TO ITS REAL HEAT CONSUMPTION

One of the most important issues in the implementation of energy saving measures is a proper evaluation of possible energy savings. If energy savings are overestimated in an energy audit (EA), a situation may occur where after the renovation, the implemented energy saving measures is not paid back or their pay back time is longer than expected before the funds (mostly loaned) were invested. To avoid such a situation, the procedure of a building's energy audit should involve the correction of calculated heat balance according to its real heat consumption, recalculated to the nonnative conditions. In manipulating different building parameters of not exact meanings, it is necessary to attain that the building's heat demand before renovation (theoretically calculated by the same methodology and parameters as demand after renovation) would be as close as possible to the actual heat consumption, recalculated under normative conditions. Only after such a fitting of the actual and theoretical heat demands (decomposition of building heat balance and correction of its components) is it possible to have a reasonable assessment of the feasible heat savings, after the implementation of heat saving measures. The aim of this work is to disclose some peculiarities of building heat balance that is used for energy audit calculations of existing buildings, to offer a calculation methodology evaluating these peculiarities, to show evidently the importance of the investigated problem.

CORRECTION OF A DESIGNED BUILDING'S HEAT BALANCE ACCORDING TO ITS REAL HEAT CONSUMPTION

One of the most important issues in the implementation of energy saving measures is a proper evaluation of possible energy savings. If energy savings are overestimated in an energy audit (EA), a situation may occur where after the renovation, the implemented energy saving measures is not paid back or their pay back time is longer than expected before the funds (mostly loaned) were invested. To avoid such a situation, the procedure of a building's energy audit should involve the correction of calculated heat balance according to its real heat consumption, recalculated to the nonnative conditions. In manipulating different building parameters of not exact meanings, it is necessary to attain that the building's heat demand before renovation (theoretically calculated by the same methodology and parameters as demand after renovation) would be as close as possible to the actual heat consumption, recalculated under normative conditions. Only after such a fitting of the actual and theoretical heat demands (decomposition of building heat balance and correction of its components) is it possible to have a reasonable assessment of the feasible heat savings, after the implementation of heat saving measures. The aim of this work is to disclose some peculiarities of building heat balance that is used for energy audit calculations of existing buildings, to offer a calculation methodology evaluating these peculiarities, to show evidently the importance of the investigated problem. First Published Online: 26 Jul 2012

Calculation of building heating demand in EPIQR

Calculations of energy requirements for space heating in EPIQR are based on an existing computer programme, made according to the European standard EN 832:1998. The programme was originally a stand-alone programme with its own user interface. This has been stripped of and the source code re-compiled into a dynamic link library (DLL) controlled by EPIQR. The method is based on a monthly calculation of heat losses and usable heat gains for the building. For the calculation, the monthly mean values of the external temperature and solar radiation are applied, and the heat gain from lighting and appliances, as well as the heat-accumulating capacity of the building, are taken into consideration. In EPIQR, some input parameters have been fixed to ensure that the user only has to supply simple input data to carry out a heating requirement calculation. This paper describes the applied calculation technique and the assumptions made in EPIQR to carry out heating requirement calculations and how energy-saving retrofit is evaluated using the software.

Pearl luster pigments as overheating protection in transparently insulated solar façades

Transparently insulated (TI) walls are an efficient means to reduce the heating demand of buildings. However, large scale use of TI is still not realized, basically due to overheating problems. Mechanical shading devices are expensive and may malfunction. Furthermore, the lack of acceptance from architects because of the missing color-designability remains an unsolved problem. A promising solution for both mentioned points is a coating of pearl luster pigments on the TI wall. These pigments show an angle-dependent transmittance and reflectance and their color is variable. The pigments are structured similarly to natural pearls, where the color is caused by an interference effect of multiple layers with alternating refractive indices. A model for radiation transfer in the pigments has been derived and verified experimentally. The model can be used to design pigments with tailor-made properties. Based on insolation data from the test reference year for Wuerzburg, Germany (TRY05), the ideal cut-off angle which depends on the latitude has been calculated for a middle-European location, considering direct and diffuse solar radiation. This allows to derive the energy savings potential of TI walls covered with optimized pearl luster pigments. Finally, a 1.6×2.4 m 2 glass cover, equipped with selected pigments, was installed at the ZAE test facility in Wuerzburg. These experiments show that the heat flux into the room in summer is reduced drastically and overheating can be prevented.

A method for predicting the annual building heating demand based on limited performance data

In this paper, we present an investigation of the possibility to use a neural network combined with a quasi-physical description in order to predict the annual supplied space heating demand ( P) for a number of small single family buildings located in the North of Sweden. As a quasi-physical description for P, we used measured diurnal performance data from a similar building or simulated data from a steady state energy simulation software. We show that the required supplied space heating demand may be predicted with an average accuracy of 5%. The predictions were based on access to measured diurnal data of indoor and outdoor temperatures and the supplied heating demand from a limited time period, ranging from 10 to 35 days. The prediction accuracy was found to be almost independent of what time of the year the measurements were obtained from, except for periods when the supplied heating demand was very small. For models based on measurements from May and fo some buildings from April and September, the prediction was less accurate.