• Energy Research

Energy simulation programs are commonly used to calculate the climate and energy requirements in glazed spaces and adjacent buildings. However, these programs have usually been developed to study buildings with ordinary window sizes. Comparisons of four simulation programs were carried out for a sunspace with an adjacent room. The distribution of solar radiation between the glazed space and the adjacent room as well as the portion of short wave radiation lost to the outside were studied. The programs show very large differences. The more simple calculation methods overestimate the utilization of solar radiation. This means that the temperature in the glazed space and also cooling requirements will be overestimated. In addition, heating requirements will be underestimated. The investigation shows that simulations of glazed spaces must be based on a geometrical description of the buildings, taking into account transmission through windows, reflection and absorption.

Reducing energy use in buildings is essential to decrease the environmental impact. Outside Gothenburg in Sweden, 20 terrace houses were built according to the passive house standard and completed in 2001. The goal was to show that it is possible to build passive houses in a Scandinavian climate with very low energy use and to normal costs. The houses are the result of a project including research, design, construction, monitoring and evaluation. The passive house standard means that the space heating peak load should not exceed 10 W/m(2) living area in order to use supply air heating. This requires low transmission and ventilation losses and the building envelope is therefore highly insulated and very airtight. A mechanical ventilation system with approximately 80% heat recovery is used. The electric resistance heating in the supply air is 900 W per living unit. Solar collectors on the roof provide 40% of the energy needed for the domestic hot water. The monitored delivered energy demand is 68 kWh/m(2) a. Energy simulations show that main differences between predicted and monitored energy performance concern the household electricity and the space heating demand. Total delivered energy is approximately 40% compared with normal standard in Sweden.

This paper presents energy and environmental performance analyses, a study of summer indoor temperatures and occupant behavior for an eight story apartment building, with the goal to combine high energy efficiency with low environmental impact, at a reasonable cost. Southern Portvakten building is built with prefabricated timber elements using passive house principles in the North European climate. Energy performance was analyzed through parametric studies, as well as monitored energy data, and complemented with analysis of occupant behavior during one year. Results show that airtight, low-energy apartment buildings can be successfully built with prefabricated timber elements in a cold climate. The monitored total energy use was 47.6 kWh/m2, excluding household electricity (revised to a normal year), which is considerably lower than of a standard building built today in Sweden—90 kWh/m2. However, the occupancy level was low during the analyzed year, which affects the energy use compared to if the building had been fully occupied. Environmental analysis shows that the future challenges lie in lowering the household and common electricity use, as well as in improving the choices of materials. More focus should also lie on improving occupant behavior and finding smart solar shading solutions for apartment buildings.

An increasing demand for energy-efficient buildings has led to an increasing focus on predicted energy performance once a building is in use. Many studies have identified a performance gap between predicted energy use and actual measured energy use once buildings are in the user phase. However, none of the identified studies normalise measured energy use for both internal and external deviating boundary conditions. This study uses a Net-zero energy building (Net ZEB) building in Sweden to test two different approaches to the normalisation of measured energy use—static and dynamic methods. The normalisation of energy use for a ground source heat pump reduces the performance gap from 12% to 1–5%, depending on the method of normalisation. The normalisation of energy from photovoltaic (PV) panels reduces the performance gap from 17% to 5%, regardless of the method used. The results show that normalisation is important in order to accurately determine the energy performance of buildings. The most important parameters are the indoor temperature and internal loads, which have the largest effect on normalisation in this case study. Furthermore, the case study shows that it is possible to build Net ZEB buildings with existing technologies in a Northern European climate.

Abstract This work, framed in the IEA SHC Task 51 “Solar Energy in Urban Planning”, presents an illustrative perspective of solar energy in urban planning through the analysis of 34 international case studies conducted in 10 countries. The aim here is to examine challenges, barriers and opportunities for active solar systems and passive solar strategies by taking into consideration interrelated technical and non-technical aspects in ongoing and completed projects. It focuses on exposing potential pitfalls and illustrating lessons learned in case studies divided into three categories: (i) existing urban areas, (ii) new urban areas, and (iii) solar landscapes. The analysis has yielded insights into the solar energy strategy adoption, the evaluation of solar energy production, solar irradiation and daylighting, and the architectural quality, sensitivity and visibility of the solar systems for urban planning. The outcomes have implications to stimulate successful practices in implementing solar strategies in urban planning and facilitating their replicability worldwide by avoiding common mistakes.

AbstractOur existing urban environment has a significant potential to increase the use of renewable energy, mainly by using solar irradiation for heat and electricity. Quantification of the solar potential by means of a solar map is the first step in the acceleration process for using more solar energy in our urban environments. A solar map is a GIS system providing the annual solar irradiation on building surfaces, mostly accompanied by information of the output of solar thermal or photovoltaic systems. Many solar maps are already in place today; almost all of them are however using different approaches. In this paper, an analysis is done of current solar maps in order to see on which principles the solar maps were based upon.

AbstractThere is an urgent need to start generating energy within cities in order to pave the way for a more sustainable and resilient society. Renewable energy by means of active solar energy systems (solar thermal, ST and/or photovoltaics, PV) can be generated using roofs and facades of buildings. In this study, the annual solar energy potential of typical Swedish city blocks was analysed in order to develop guidelines for urban planners and architects. The results show that the design of the city blocks has a significant effect (up to 50%) on the total annual solar energy production. The study also shows that the contribution from active solar energy can be significant even in the urban environment, but shading by adjacent buildings may greatly limit the total amount of energy produced.

A generally accepted way of building passive houses has been to have small windows facing north and large windows to the south. This is to minimize losses on the north side while gaining as much solar heat as possible on the south. ln spring 2001, 20 terraced houses were built outside Gothenburg partly in this way. The indoor temperature is kept at a comfortable level by passive methods, using solar gains and internal gains from household appliances and occupants. Heat losses are very low, since the building envelope is well insulated and since modem coated triple-glazed windows have been installed. The purpose of this work was to investigate how decreasing the window size facing south and increasing the window size facing north in these low energy houses would influence the energy consumption and maximum power needed to keep the indoor temperature between 23 and 26 degrees C. Different orientations have been investigated as well as the influence of window type. A dynamic building simulation tool, DEROB-LTH, was used and the simulations indicate an extremely low energy demand for the houses. The results show that the size of the energy efficient windows does not have a major influence on the heating demand in the winter, but is relevant for the cooling need in the summer. This indicates that instead of the traditional way of building passive houses it is possible to enlarge the window area facing north and get better lighting conditions. To decrease the risk of excessive temperatures or energy needed for cooling, there is an optimal window size facing south that is smaller than the original size of the investigated buildings. (C) 2005 Elsevier B.V. All rights reserved. (Less)