Can PV or solar thermal systems be cost effective ways of reducing CO 2 emissions for residential buildings?

This paper compares two solar systems, an actual building integrated, photovoltaic roof (BIPV) and a notional solar thermal system for a residential block in London, UK. The carbon payback for the solar thermal system is 2 years, the BIPV system has a carbon payback of 6 years. Simple economic payback times for both systems are more than 50 years. Calculations considering the current UK energy price increase (10%/yr), reduce the economic payback time for the PV roof to under 30 years.The costs to reduce overall carbon dioxide emissions using a BIPV roof are £196/tonne CO2, solar thermal individual systems at £65/tonne CO2 and community solar thermal at £38/tonne CO2. The current spot market price for CO2 is £15/tonne CO2 (20). Capital costs for PV systems in particular must be significantly reduced for them to be a cost-effective way to reduce CO2. This paper compares two solar systems, an actual building integrated, photovoltaic roof (BIPV) and a notional solar thermal system for a residential block in London, UK. The carbon payback for the solar thermal system is 2 years, the BIPV system has a carbon payback of 6 years. Simple economic payback times for both systems are more than 50 years. Calculations considering the current UK energy price increase (10%/yr), reduce the economic payback time for the PV roof to under 30 years.The costs to reduce overall carbon dioxide emissions using a BIPV roof are £196/tonne CO2, solar thermal individual systems at £65/tonne CO2 and community solar thermal at £38/tonne CO2. The current spot market price for CO2 is £15/tonne CO2 (20). Capital costs for PV systems in particular must be significantly reduced for them to be a cost-effective way to reduce CO2

Is photovoltaic power a cost-effective energy solution for rural peoples in western Sudan?

Sudan like most poor countries suffers from a deficiency in the supply of electrical power, especially for rural areas. Less than 10% of the total population, can benefit from the national grid connection. The paper evaluates the economic, environmental and social issues associated with electrification in western Sudan for rural and nomadic peoples, by assessing three different systems for off-grid electricity supply; stand alone systems powered by diesel generator (gen-set), photovoltaic cells, and a larger distributed generator system (mini-grid). The study indicates that, although photovoltaic might be the best source of electricity from an environmental and social view, unfortunately it currently cannot compete economically. The research identified that Sudanese customs and tax policy adds a significant cost to PV, making diesel generators the best power choice for rural and nomadic regions in Sudan. Other important factors include fuel supply problems and availability of spare parts for generators

Lessons learned from the Pefki solar village in Athens, nearly 20 years on

Solar Village 3 in Pefki, Athens, was part of an ambitious program, with active and passive solar systems providing space and water heating for 1750 inhabitants, designed in the early 80's, and inhabited from the late 80's. This paper focuses on passive solar systems applied to a number of the buildings. A survey highlighted the cases of trombe water benches and conservatories as the most frequently, poorly operated systems. Over time this led to a lack of belief by the occupants in the passive systems. Building simulation indicated a much higher cooling load than originally designed for, combined with recent warmer summers and poor maintenance and operation, have led to the present case that many homes have installed air conditioning. Plans for district heating will improve heating provision for residents and reduce CO2 emissions but a lack of a maintenance strategy for the passive systems will surely lead to their increased neglect

Ventilation of double facades

This paper deals with the development and thetesting of a simulation algorithm for the temperaturebehaviour and the flow characteristics of doublefaçades. It has been developed in order to obtain atool which enables the energy consultant to makequick design decisions without being required to usefairly complicated CFD tools.In order to determine the degree of accuracy of thealgorithm, a double façade has been monitored undercontrolled conditions and the results have beencompared against the predicted values for severaldesign situations. The resulting inaccuracy in somecases can be traced back to how the flow resistanceof various geometries are modelled. This paper deals with the development and thetesting of a simulation algorithm for the temperaturebehaviour and the flow characteristics of doublefaçades. It has been developed in order to obtain atool which enables the energy consultant to makequick design decisions without being required to usefairly complicated CFD tools.In order to determine the degree of accuracy of thealgorithm, a double façade has been monitored undercontrolled conditions and the results have beencompared against the predicted values for severaldesign situations. The resulting inaccuracy in somecases can be traced back to how the flow resistanceof various geometries are modelled

Data visualization within urban models

Models of urban environments have many uses for town planning, pre-visualization of new building work and utility service planning. Many of these models are three-dimensional, and increasingly there is a move towards real-time presentation of such large models. In this paper we present an algorithm for generating consistent 3D models from a combination of data sources, including Ordnance Survey ground plans, aerial photography and laser height data. Although there have been several demonstrations of automatic generation of building models from 2D vector map data, in this paper we present a very robust solution that generates models that are suitable for real-time presentation. We then demonstrate a novel pollution visualization that uses these models

Preventive conservation strategies for sustainable urban pollution control in museums

The last 40 years have seen major changes in the sources and concentrations of urban pollution (nitrogen dioxide, sulfur dioxide, hydrogen sulfide, and particulates). During this time, research has advanced our understanding of the impact of pollutants on objects in urban museums. As a consequence, pollutant control has become an important aspect of preventive conservation. There is also increased awareness of the need for pollution control strategies that are sustainable at an organizational and global level. This report, prepared by a chemist, a conservator, and two building scientists, reviews strategies for minimizing the impact of urban pollution on museum collections. The results of new research funded by the UK government identify current (1999) internal pollution levels in both naturally ventilated and air-conditioned museums with particle and gaseous filtration, in relation to external concentrations, ventilation strategies, and the characteristics of the internal fabric and finishes of these buildings. The last 40 years have seen major changes in the sources and concentrations of urban pollution (nitrogen dioxide, sulfur dioxide, hydrogen sulfide, and particulates). During this time, research has advanced our understanding of the impact of pollutants on objects in urban museums. As a consequence, pollutant control has become an important aspect of preventive conservation. There is also increased awareness of the need for pollution control strategies that are sustainable at an organizational and global level. This report, prepared by a chemist, a conservator, and two building scientists, reviews strategies for minimizing the impact of urban pollution on museum collections. The results of new research funded by the UK government identify current (1999) internal pollution levels in both naturally ventilated and air-conditioned museums with particle and gaseous filtration, in relation to external concentrations, ventilation strategies, and the characteristics of the internal fabric and finishes of these buildings

The effect of climate change on office building energy consumption in Japan

Global climate change is making the mild Japanese climate significantly warmer, which is expected to have a substantial impact on building energy consumption. The potential impacts of climate change on the cooling and heating loads for offices are also investigated by means of thermal analysis simulations at three sites over three periods; 1981–2000, 2031–2050, and 2081–2100. This study reveals that under the IPCC’s A2 carbon emission scenario, substantial reductions of energy consumption are expected if the full measures reviewed here are implemented. These rates differ in each location and each period due to regional climate characteristics and climate change. CO2 emissions reduction targets will depend on future electricity conversion factors which could worsen due to revisions of the national energy plan triggered by the Fukushima nuclear accident. Japan still has a vast quantity of energy inefficient old offices (pre-1981). With more specific and up-to-date technologies than those reviewed here, even greater energy reductions could be completed. A brief economic analysis suggests that these measures could be competitive with nuclear power generation. Overall, office buildings in Japan have enormous potential to reduce energy requirements and related CO2 emissions without resorting to nuclear power generation

Suspended timber ground floors: measured heat loss compared with models

There are approximately 6.6 million dwellings in the UK built before 1919, predominantly constructed with suspended timber ground floors whose thermal performance has not been extensively investigated. The results are presented from an in-situ heat-flow measuring campaign conducted at 27 locations on a suspended timber ground floor, and the estimated whole-floor U-value compared with modelled results. Findings highlight a significant variability in heat flow, with increased heat loss near the external perimeter. In-situ measured-point U-values ranged from 0.54 ± 0.09 Wm−2 K−1, when away from the external wall perimeter, to nearly four times as high (2.04 ± 0.21 Wm−2 K−1) when near the perimeter. The results highlight the fact that observing only a few measurements is likely to bias any attempts to derive a whole-floor U-value, which was estimated to be 1.04 ± 0.12 Wm−2 K−1 and nearly twice that derived from current models. This raises questions about the validity of using such models in housing stock models to inform retrofit decision-making and space-heating-reduction interventions. If this disparity between models and measurements exists in the wider stock, a reappraisal of the performance of suspended timber ground floors and heat-loss-reduction potential through this element will be required to support the UK’s carbon-emission-reduction targets