Articles

State of the Irish Housing Stock - Modelling the heat losses of Ireland’s existing detached rural housing stock & estimating the benefit of thermal retrofit measures on this stock

Ciara Ahern et al. — Fri, 25 Jan 2013 08:05:31 PST

Ireland’s housing stock has been identified as being amongst the least energy efficient in Northern Europe. Consequently, atmospheric emissions are greater than necessary. Government funded schemes have been introduced to incentivise the uptake of thermal retrofit measures in the domestic Irish market. A study of Ireland’s housing highlights the dominance of detached houses (43%), 72% of which are rurally located and are predominantly heated with fuel oil. This paper investigates the economic and carbon case for thermal retrofit measures to the existing detached, oil centrally heated, rural housing stock. The study found the case for energy efficiency measures to be categorical and supports the Irish Government’s focus on energy efficiency policy measures. Thermal retrofit measures in the detached housing stock have the potential to realise an averaged 65% theoretical reduction in heating costs and CO₂ emissions for houses constructed prior to 1979 (coinciding with the introduction of building regulations) and around 26% for newer homes, thus offering a significant contribution (44%) to Ireland’s residential carbon abatement projections and hence in meeting the EU’s directives on energy and carbon. The greatest savings (36%) of Ireland’s carbon abatement projections result from improving the energy efficiency of the pre 1979 stock.

Repointing Mortars for Conservation of a Historic Stone Building in Trinity College, Dublin

Simon H. Perry et al. — Mon, 05 Nov 2012 07:55:26 PST

With atmospheric pollution causing building stone to decay at accelerated rates, conservation of historic stone monuments is becoming an increasingly important issue. Mortar joints have a marked effect on how moisture moves in a wall and, hence, on how the wall weathers. Not only does mortar bind stones together, but also a good mortar will prevent the ingress of moisture (and pollutants), enable the buildings to dry out, accommodate movement and will not act as a source of harmful chemicals capable of attacking the surrounding stone. Thus, poor mortar can have deleterious effects on the stonework. This paper, which is the result of research sponsored by the Commission of European Communities, considers a number of commonly used, and some more rarely used, pointing mortars, and assesses them with a view to using the most successful for repointing a historic stone building in Trinity College, Dublin.

Repointing Mortars for Conservation of a Historic Stone Building in Trinity College, Dublin

Aidan Duffy et al. — Mon, 05 Nov 2012 07:55:25 PST

Physicochemical and Microbiological quality of harvested rainwater from an agricultural installation in Ireland

sean O'Hogain et al. — Tue, 11 Sep 2012 04:42:14 PDT

Members of DTC Research Group. Dublin Institute of Technology was commissioned in 2005 by the Department of Environment, Heritage and Local Government in Ireland to assess the feasibility of utilising rainwater to replace treated mains water for nonpotable uses. The project involved the design, installation, commissioning and monitoring of rainwater harvesting on a farm. Two monitoring programmes, Regime 1 and Regime 2, examined the physicochemical and microbiological quality of the harvested rainwater. Samples were taken monthly and tested. Regime 1 analysis showed that the microbiological quality of the rainwater from the site did not comply with the requirements of the European Communities Quality of Bathing Water Regulations, while the physicochemical quality complied with both Bathing and Drinking Water Standards with the exception of ammonia and lead. Regime 2 results showed a signiﬁcant improvement and were compliant with the European Communities Quality of Bathing Water Regulations and showed near compliance with the European Communities Drinking Water Regulation.

Physicochemical and microbiological quality of water from a pilot domestic rainwater harvesting facility in Ireland.

Sean O'Hogain et al. — Tue, 11 Sep 2012 04:42:13 PDT

DTC Research Group, Dublin Institute of Technology personnel were commissioned in 2005 by the Department of Environment, Heritage and Local Government in Ireland to assess the feasibility of utilising harvested rainwater to replace treated mains water, for non-potable uses. A pilot project was set up. The project involved the design, installation, commissioning and monitoring of rainwater harvesting facilities in a rural housing development. A monitoring program was carried out to examine the physico-chemical and microbiological quality of the harvested rainwater. Harvested rainwater was sampled monthly and tested. Analysis of the harvested rainwater quality showed a consistently high quality of raw water in general compliance with the requirements of the European Communities (Quality of Bathing Water) Regulations for 100 % of samples and the European Communities (Drinking Water) Regulations, 2007 for 37% of sampling dates

Enhancement Factors for the Vertical Response of Footbridges Subjected to Stochastic Crowd Loading

Colin C. Caprani et al. — Tue, 11 Sep 2012 04:42:11 PDT

The vertical acceleration response of a hypothetical footbridge is predicted for a sample of single pedestrians and a crowd of pedestrians using a probabilistic approach. This approach uses statistical distributions to account for the fact that pedestrian parameters are not identical for all pedestrians. Enhancement factors are proposed for predicting the response due to a crowd based on the predicted accelerations of a single pedestrian. The significant contribution of this work is the generation of response curves identifying enhancement factors for a range of crowd densities and synchronization levels.

A Review of Zero Discharge Wastewater Treatment Systems Using Reed Willow Bed Combinations in Ireland

Sean O'Hogain et al. — Fri, 20 Apr 2012 04:22:49 PDT

The concept of a reed willow bed combination has the potential to achieve a zero discharge wastewater treatment system. This paper will present results from a two year study to monitor the performance of a reed willow bed facility at Lynches Lane, Co. Dublin, Ireland. Outline design specifications for the facility will be presented. Monitoring results for a two year period including influent and effluent parameters, rainfall, potential evapotranspiration, and soil classification will be presented and discussed. During the two year monitoring period the system achieved a zero discharge. This paper will discuss the potential widespread application of similar systems in Ireland. This is in the context of a recent EU judgment which declared that Ireland has failed to fulfill its obligations regarding domestic wastewaters disposed of through individual waste water treatment systems. The development of an appropriate zero discharge wastewater facility has the potential to address this source of environmental pollution in Ireland. This paper will discuss the sizing and operation of such systems specific to the climate and soil conditions based on current knowledge and experience. Areas for further studies will be discussed.

Rebuilding after Disaster - Engineering Lessons from the 2004 Tsunami

Liam McCarton — Fri, 20 Apr 2012 04:22:08 PDT

On 26th December 2004 a magnitude 9 earthquake occurred off the west coast of northern Sumatra, Indonesia. The sudden and violent vertical displacement of the sea floor caused a disturbance to the overlying water column, which generated waves (tsunami) that propagated rapidly across the whole of the Indian Ocean. Typically, in open ocean waters, these waves have long wavelengths of the order of 200km and low trough to crest amplitudes. These properties allow them to conserve energy as they propagate over large distances. As the waves enter the shallower waters of coastal areas, their amplitude increases dramatically and their velocity reduces, resulting in violent wave impacts and extensive flood inundation inland. Unprepared for such a natural disaster and with no warning systems in place, more than 225,000 people died in South and Southeast Asia, and several million were left homeless. Liam McCarton, worked in Sri Lanka from 2005 to 2007 as Project Manager for post tsunami reconstruction programs. In this article he discusses some of the technical and humanitarian challenges involved in managing a reconstruction program in a developing country and presents some of the lessons learnt.

Rainwater Harvesting and Grey Water Recycling Systems

Liam McCarton et al. — Mon, 16 Apr 2012 08:49:44 PDT

The benefits of water efficiency measures, rainwater harvesting and greywater reuse are principally water savings and reduced volume of consumption. Cost savings can accrue to the water supplier and water user. These benefits can be felt at a local level. Only with widespread use of such technology will reduced pressure on water resources and the supply infrastructure be realised. These technologies should be considered in the context of an overall water conservation strategy and each situation evaluated separately. A water audit should be undertaken to establish existing water usage and possible demands that can be met by using these technologies. A programme to develop public awareness and to source and promote these technologies is also required. Standards for fittings and legal standards for rainwater quality are required if these technologies are to become generally installed. The use of these technologies should be driven by the need to develop a sustainable strategy of urban water demand management.

Water Conservation and Resuse Strategy for Ireland

Liam McCarton et al. — Mon, 16 Apr 2012 08:49:43 PDT

The traditional approach to meeting increased demand is to augment supply. However, mobilising new resources involves ever higher costs. Increasing water efficiency by reducing the amount of water required to accomplish a given task can significantly contribute towards balancing supply and demand. The water saved as a result of PCC reduction can be used to augment existing supplies. This can be the least cost option, particularly when the environmental and social costs of developing new resources are included in the analysis. Allied to this is the concept of sustainability, which can be defined as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’. An important consideration in itself, sustainability forms a major part of the EU water strategy outlined in the Water Framework Directive 2000. The concept of water conservation and water saving technologies are set to play a major role in our lives.

Water Conservation Technologies

Liam McCarton — Mon, 16 Apr 2012 07:51:38 PDT

Given the increasing incidence of serious flooding in Europe in recent years it might seem odd to be addressing the problem of water conservation. However, recent economic prosperity has led to an increased per capita use of water for domestic and industrial use. The traditional approach to meeting increased demand is to augment supply. However, mobilising new resources involves ever higher costs. Allied to this is the concept of sustainability, which can be defined as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’. An important consideration of itself, sustainability forms a major part of the new EU water strategy outlined in the Water Framework Directive 2000, which member states have 3 years to transpose into national legislation. Therefore, the concept of water conservation and water saving technologies are set to play a major role in our lives. Increasing the rate of water efficiency requires a multi-dimensional approach that can be achieved by adopting alternative technologies. The application of these technologies is further facilitated by the growth in urbanization and the scale of change in demand patterns.

Comparative Field Performance Study of Flat Plate and Heat Pipe Evacuated Tube Collectors (ETCs) for Domestic Water Heating Systems in a Temperate Climate

Lacour Ayompe et al. — Tue, 28 Feb 2012 07:39:28 PST

This paper presents a year round energy performance monitoring results of two solar water heaters with 4 m² flat plate and 3 m² heat pipe evacuated tube collectors (ETCs) operating under the same weather conditions in Dublin, Ireland. The energy performance of the two systems was compared on daily, monthly and yearly basis. Results obtained showed that for an annual total in-plane solar insolation of 1,087 kWh/m², a total of 1,984 kWh and 2,056 kWh of heat energy were collected by the 4 m² FPC and 3 m² ETC systems respectively. Over the year, a unit area of the FPC and ETC each generated 496 kWh/m² and 681 kWh/m² of heat respectively. For 3149.7 kWh and 3053.6 kWh of auxiliary energy supplied to the FPC and ETC systems their annual solar fractions (SFs) were 38.6% and 40.2% respectively. The annual average collector efficiencies were 46.1% and 60.7% while the system efficiencies were 37.9% and 50.3% respectively for the FPC and ETC respectively. Economic analysis showed that both solar water heating (SWH) systems are not economically viable with NPVs ranging between -€4,264 and -€652 while simple payback periods (SPPs) varied between 13 years and 48.5 years.

Validated TRNSYS Model for Forced Circulation Solar Water Heating Systems with Flat Plate and Heat Pipe Evacuated Tube Collectors

Lacour Ayompe et al. — Tue, 28 Feb 2012 07:31:59 PST

This paper presents a validated TRNSYS model for forced circulation solar water heating systems used in temperate climates. The systems consist of two flat plate collectors (FPC) and a heat pipe evacuated tube collector (ETC) as well as identical auxiliary components. The systems were fitted with an automated unit that controlled the immersion heaters and hot water demand profile to mimic hot water usage in a typical European domestic dwelling. The main component of the TRNSYS model was the Type 73 FPC or Type 538 ETC. A comparison of modelled and measured data resulted in percentage mean absolute errors for collector outlet temperature, heat collected by the collectors and heat delivered to the load of 16.9%, 14.1% and 6.9% for the FPC system and 18.4%, 16.8% and 7.6% for the ETC system respectively. The model underestimated the collector outlet fluid temperature by -9.6% and overestimated the heat collected and heat delivered to load by 7.6% and 6.9% for the FPC system. The model overestimated all three parameters by 13.7%, 12.4% and 7.6% for the ETC system.

Heat Transfer Correlations for Low Approach Evaporative Cooling Systems in Buildings

Ben Costelloe et al. — Mon, 31 Jan 2011 08:41:49 PST

The experimental performance of an open industrial scale cooling tower, utilising small approach temperature differences (1–3 K), for rejection of heat at the low water temperatures (11–20 °C) typical of chilled ceilings and other sensible air–water heat dissipation systems in buildings, is examined. The study was carried out under temperate maritime climatic conditions (3–18 °C wet-bulb temperature range). Initially a theoretical analysis of the process at typical conditions for this climate was conducted, which indicated that a water to air (L/G) mass flow rate ratio of less than 1.0 was required for effective operation. Consequently for these low L/G ratios, the thermal performance of the experimental tower was measured and correlated. A new correlation is proposed which shows a significant increase in the NTU level achieved, for the required L/G ratios (0.3–0.9). As the cooling tower in this application is predominantly a mass transfer device under summer conditions, the evaluation of the total volumetric heat and mass transfer coefficient (kga s−1 m−3) is of particular relevance and is also determined.

Evaluation of Implicit Numerical Methods for Building Energy Simulation

Michael Crowley et al. — Wed, 26 Jan 2011 13:33:17 PST

The stability of numerical methods used for finite-difference thermal modelling of buildings is discussed. A known instability in a commonly used process is described and alternative numerical methods with suitable stability properties are identified. With a view to selecting the optimum numerical method, the building energy simulation problem is characterized mathematically and appropriate implicit solvers are compared on the basis of accuracy and computational effort using a building related test problem prepared for this purpose. A recently developed numerical method with the necessary strong stability is found to possess higher computational efficiency than methods frequently used in this application and it is recommended for inclusion in building energy simulation software.

Improved Direct Solver for Building Energy Simulation

Michael Crowley et al. — Fri, 21 Jan 2011 04:43:26 PST

Finite difference methods, when applied to the differential equations modelling energy flows in buildings, give rise to a system of non-linear difference equations. A frequently used direct solution method involving linearization is analysed and a related method proposed. These and one other connected method are compared using a building related test problem prepared for this purpose. The proposed numerical method is found to produce least error, about 30% less than the commonly used method, and it is recommended for inclusion in building energy simulation software. A fundamental method for estimating the pre conditioning period of a building, arising from the work, is discussed.

Experimental Energy Performance of Open Cooling Towers Used Under Low and Variable Approach Conditions for Indirect Evaporative Cooling of Buildings

Ben Costelloe et al. — Thu, 20 Jan 2011 08:15:28 PST

The success of chilled ceilings and displacement ventilation systems as a means of sensible cooling in buildings has prompted a review of evaporative cooling technology as an effective means of generating the required cooling water. When such cooling water is generated at low approach conditions (2–5 K), at the higher temperatures required in these systems (14–18°C), very high levels of availability result. In many north western European locations the levels of availability are such that the prospect of supplanting rather than simply supplementing the refrigeration system, for sensible cooling purposes, arises. The viability of the technique, however, largely depends on achieving low approach conditions, at acceptable levels of energy performance. Hence the need to investigate the energy performance of the process. This paper presents the results of recent experimental research into: i) the achievement of low approach conditions in an evaporative cooling test rig; and ii) the energy performance of this test rig when generating cooling water, indirectly, at the temperatures required for chilled ceilings. Energy performance is presented for a range of specifi c conditions and typical annual effi ciencies of cooling water generation are determined. Results are compared with typical energy effi ciencies of conventional, vapour compression based, refrigeration systems. A signifi cant potential for improved annual energy performance, is shown.

Thermal Effectiveness Characteristics of Low Approach Indirect Evaporative Cooling Systems in Buildings

Ben Costelloe et al. — Thu, 20 Jan 2011 08:14:52 PST

Meteorological enthalpy analysis of temperate and maritime climates above latitude 45°N suggests that the water-side evaporative cooling technique has considerable unrealised potential with contemporary “high temperature” building cooling systems—such as chilled ceilings and displacement ventilation. As low approach conditions are the key to exploiting the cooling potential of the ambient air, thermal performance at such conditions needs to be investigated. To address the research issues, an industrial scale test rig, based on a low approach open cooling tower and plate heat exchanger and designed to maximise evaporative cooling potential, has been constructed. The thermal effectiveness of such systems (as a measure of the degree to which the system has succeeded in exploiting the cooling potential of the ambient air) is a key parameter. This paper presents the results of experimental research into the thermal effectiveness of a water-side, open, indirect evaporative cooling test rig, designed to achieve low (1–4 K) approach conditions in the temperate maritime climate of northern Europe. The sensitivity of the thermal effectiveness to a series of key operating variables is investigated. High thermal effectiveness of up to 0.76 was found with both cooling tower air-flow rate and secondary water-flow rate having a strong impact. Primary water-flow rate however, has a weak impact on thermal effectiveness but a major impact on energy performance—indicating scope for a considerable improvement in energy performance at the expense of a minor reduction in thermal effectiveness. A proposed energy efficient control strategy for this form of cooling water generation is proposed and supported by an analysis of the measured results.

Indirect Evaporative Cooling Potential in Air-water Systems in Temperate Climates

Ben Costelloe et al. — Thu, 20 Jan 2011 08:14:50 PST

Recent developments have prompted a review of evaporative cooling technology as an effective means of cooling modern deep plan buildings. Prominent among these developments is the success of high temperature sensible cooling systems, particularly, chilled ceilings, which require a supply of cooling water at 14–18 °C. Crucial to the success of evaporative cooling technology, as a significant means of cooling in modern applications, is the ability to generate cooling water, in an indirect circuit, at a temperature which closely approaches the ambient adiabatic saturation temperature (AST) or wet bulb temperature (WBT). Recent experimental research has demonstrated that it is technically viable to generate such cooling water at a temperature of 3 K above the ambient AST. While the frequency of ambient AST occurrence can be obtained from meteorological sources, there is little in-depth analysis of the potential for this form of cooling water generation, based on the approach temperatures which have now been shown to be viable. The decision to use an evaporative cooling system depends largely on an assessment, in-depth, of net energy saved against capital expended. Such an assessment requires detailed data on the availability of cooling water, generated by evaporation, for each location. This paper quantifies evaporative cooling availability in-depth for a northern and southern European city, Dublin and Milan and suggests a method of analysing such data for any world wide location, for which suitable meteorological records are available. The paper, incorporates recent experimental research findings and bases the availability analysis on meteorological test reference weather year data. The results of this research confirm a major potential for the generation of cooling water by evaporative means, which can be used to provide effective cooling of deep plan buildings by means of contemporary water based sensible cooling systems, such as fan coil systems, radiant chilled ceiling panels and ceiling cooling convectors (chilled beams). While the technique offers most potential in locations with a northern European temperate climate, it has significant potential to contribute to cooling in some southern European cities, during the non-summer months and also at other times, particularly where load shaving techniques are incorporated.

Input-output Analysis of Irish Construction Sector Greenhouse Gas Emissions

Aidan Duffy et al. — Thu, 13 Jan 2011 06:20:26 PST

Ireland is committed to limiting its greenhouse gas (GHG) emissions to 113% of 1990 levels over the period 2008-12 and to 84% of 2005 levels by 2020 under the Kyoto Agreement and the EU’s ’20 20’ by 2020 respectively. National policies have targeted many industry sectors but have failed to directly tackle GHG emissions associated with construction activity. This paper estimates energy and GHG emissions intensities of the Irish construction sector and subsectors and estimates its contribution to Irish national emissions. This information is used to identify and assess the impacts of policy measures which would result in a reduction in emissions from the sector in a cost-effective manner. Energy and emissions intensities are estimated using input-output analysis techniques applied to Irish construction sector. In 2005 the Irish construction sector was responsible for the emission of 13.81mtCO2eq, comprising 2.37mt (17%) of direct on-site emissions, 5.69mt (41%) upstream indirect domestic emissions and 5.75mt (42%) upstream indirect emissions outside the state. Domestically arising direct and indirect emissions accounted for 3.44% and 8.26% of national emissions respectively. Approximately three-quarters of construction sector emissions were the result of activities relating to NACE 45.2 ‘civil and structural construction works, etc’. Given the potential importance of the construction sector to national emissions, there is scope for the implementation of policies which specifically target it. Two such policies are proposed: direct emissions mitigation through a construction EcoDriving initiative; and the provision of information to allow the design and specification of low-emissions materials.