Electricity market development in Northern Ireland

This article describes the developments of the electricity market in Northern Ireland, with emphasis on the commitment to a workable, but inexpensive, system generating minimum overheads. The focus is on the simplicity of the trading arrangements, the minimal cost of introducing these arrangements, and the criteria to be satisfied in the development of systems to meet an evolving market culture.     

Energy Design Advice Scheme: Operational experience in Northern Ireland

Services in buildings account for over 50% of UK energy consumption and almost 50% of total CO₂ emissions. Approximately one third of global ozone depletion results from the use of CFCs as refrigerants and as foaming agents for the manufacture of insulation products (Oreszczyn et al., 1994). The Energy Design Advice Scheme (EDAS) (Curtis et al., 1994) is a UK government-funded initiative that aims to improve the energy and environmental performance of the building stock. The scheme seeks to encourage the uptake of proven energy-conscious measures in building and services design, by offering free initial consultations and literature targeting specific projects and by part-funding further detailed design work. The Northern Ireland Regional Centre of the Scheme has been in operation for 2 years, during which time in the region of 200 enquiries have been received and advice given on some 45 eligible projects, of which about 15% have progressed to the funding stage. Information is given here on analysis of enquiry sources, building and customer type, building size and nature and value of project, nature of enquiry/advice given and at what stage in the design process and findings related to known operating conditions in Northern Ireland.     

Exploring the role of reanalysis data in simulating regional wind generation variability over Northern Ireland

As wind generation increases, system impact studies rely on predictions of future generation and effective representation of wind variability. A well-established approach to investigate the impact of wind variability is to simulate generation using observations from 10 m meteorological mast-data. However, there are problems with relying purely on historical wind-speed records or generation histories: mast-data is often incomplete, not sited at a relevant wind generation sites, and recorded at the wrong altitude above ground (usually 10 m), each of which may distort the generation profile. A possible complimentary approach is to use reanalysis data, where data assimilation techniques are combined with state-of-the-art weather forecast models to produce complete gridded wind time-series over an area.Previous investigations of reanalysis datasets have placed an emphasis on comparing reanalysis to meteorological site records whereas this paper compares wind generation simulated using reanalysis data directly against historic wind generation records. Importantly, this comparison is conducted using raw reanalysis data (typical resolution ∼50 km), without relying on a computationally expensive “dynamical downscaling” for a particular target region. Although the raw reanalysis data cannot, by nature of its construction, represent the site-specific effects of sub-gridscale topography, it is nevertheless shown to be comparable to or better than the mast-based simulation in the region considered and it is therefore argued that raw reanalysis data may offer a number of significant advantages as a data source.     

An investigation into the potential of low head hydro power in Northern Ireland for the production of electricity

The maximum exploitable potential for low head hydroelectric sites (gross head≤10 m) in Northern Ireland (NI) was determined as 12.07 MW using a simple payback analysis for 304 potential sites investigated to derive a classification scheme in terms of economic viability. A techno-economic analysis with validated numerical models from previous research estimated the capital investment required for the development of a hydroelectric plant, using the low head Michell-Banki cross flow turbine, for the 304 sites investigated. The number of potentially viable sites in NI for low head hydro ranged from 198 to 286 with an estimated installed capacity ranging from 11.95 to 12.05 MW. Sites with a limited installed capacity were not economically viable unless increased government support in the form of longer term (25–50 years) low interest loans as well as the current (Renewables Obligations Certificates) Renewables Obligation Certificates scheme is provided and sustained.     

An agro-economic analysis of willow cultivation in Poland

Bioenergy is recognized as the most important renewable energy source in Poland in several national policy documents. This has spurred an in increasing interest in energy crops, particularly willow, due to the large areas of arable land in Poland. However, in order for willow to be adopted by farmers, this crop must be perceived to be at least as profitable as cereal crops, such as wheat and barley, which compete for the same land. The objective of this study was to calculate the economics of growing willow on relatively large farms from a farmer's perspective in Poland. An additional objective was to relate the viability of growing willow to that of growing wheat and barley. Our calculations show that growing willow can indeed be an economically viable alternative to wheat and barley. At the current Polish price of wood chips (about 33 PLN/MWh or 7.5 €/MWh), the viability of willow is similar to that of barley given our assumptions on yields, etc. Wheat is the most viable crop of the three crops studied. Willow, however, is more profitable than both wheat and barley assuming a wood chip price of 50 PLN/MWh (11 €/MWh), which better represents the price in Europe as a whole. Despite good viability, willow is unlikely to be adopted by a great number of farmers without active support mechanisms and long-term stability of the status of energy crops in the Polish and the EU common agricultural policy.     

Biomass potentials of miscanthus,willow and poplar: results and policy implications for Eastern Europe,Northern and Central Asia

Over the past 20 years, the term agro-ecological zones methodology (AEZ) has become widely used for global regional and national assessments of agricultural potentials. The AEZ methodologies and procedures have recently been extended and newly implemented to make use of the latest digital geographical databases. At the same time a companion model of AEZ has been developed that enables assessments of potential productivity of forest tree species.AEZ follows an environmental approach; provides a standardized framework for the characterization of climate, soil and terrain conditions relevant to crop and forest species production; uses environmental matching procedures to identify limitations of prevailing climate, soil and terrain for assumed management objectives.The AEZ model includes an inventory of ecological adaptability characteristics as well as an inventory of specific ecological and environmental requirements for crop and forest tree species. The natural resources inventory is based on an up-to-date GIS database of climate, soil, terrain and vegetation covering China, Europe, Mongolia and the former Soviet Union.Results of potential productivity for miscanthus, willow and poplars in countries of Eastern Europe and Northern and Central Asia are presented for (i) all suitable areas, (ii) all suitable areas but excluding forests, urban areas and land that is potentially highly suitable for cereal production. The results show a large variation in potentials for bio-energy in the various countries. In a few countries—Lithuania, Latvia, Romania, Georgia, Belarus and Azerbaijan, the potential for producing energy from miscanthus, poplar and willow alone is more than one-third of the current commercial energy use in these countries, even when forests and land potentially highly suitable for cereals are excluded from the assessment.     

The influence of canopy density on willow leaf rust (Melampsora epitea) severity in willow short rotation coppice

Willow short rotation coppice is used as a renewable energy source and also as a vegetation filter for purifying wastewater. Wastewater irrigation might change microclimatic conditions and increase the canopy density in plantations, which might decrease production due to leaf rust (Melampsora epitea). The aim of this study was to estimate the impact of the canopy density on rust abundance on willows. For that, we counted rust pustules on leaves of five different willow clones from dense and sparse areas in both the wastewater irrigated and control part of the plantation. The results demonstrated clear differences between clones; clone ‘81090’ was very susceptible, ‘78183’ susceptible, ‘78021’ fairly tolerant and ‘Tora’ rust resistant. Clone ‘Gudrun’, which was previously reported resistant, had severe rust damages in Estonia. In the case of clones ‘78183’ and ‘78021’ there were significantly more rust pustules per leaf unit area at areas with denser canopy, which confirmed that higher plant density could result in biomass losses caused by leaf rust. No differences, however, were detected between dense and sparse areas of hybrid clone ‘Gudrun’, most probably because in this particular case leaves from upper canopy layer were used. There was a tendency detected that clones with a higher number of shoots per plant had more rust damages on their leaves, however, the correlation was not statistically confirmed. In conclusion, the impact of canopy density on rust abundance is clone-specific and significant in the case of clones on which infection starts from the lower part of the canopy.     

Environmental and hygienic aspects of willow coppice in Sweden

Willow coppice of various Salix spp. has been shown to be a good alternative to fossil fuels both environmentally and economically. Willow stands have also been shown to be adaptable as vegetation filters in order to purify waters and soils. The purification efficiency of willow vegetation filters has been demonstrated in several countries, e.g. Sweden, Poland, Denmark, and Estonia. However, there are still many questions to be answered: for example, what are the mechanisms behind the uptake and allocation of heavy metals and recalcitrant organic constituents, which maximum doses are possible in a particular situation without risks for leakage, and how are hygienic aspects influenced when using vegetation filters. The aim of this paper is to point out some relevant facts concerning willow coppice in general and willow vegetation filters in particular. More specifically, the paper presents and discusses the direct and indirect factors that are improved in such a way that there is a clear benefit of short-rotation forestry. For example, willow cultivations enhance biodiversity compared with conventional agricultural crops and monospecific conifer plantations. They have a pronounced capacity to take up nutrients and heavy metals (including cadmium). The economy is favourable regardless whether the coppice is used as biofuel or as a vegetation filter. The conclusion is that the growing and use of willow coppice is beneficial for the environment and may come to play an important role in a society based on recycling principles.     

Smart meter devices and the effect of feedback on residential electricity consumption: Evidence from a natural experiment in Northern Ireland

Using a unique set of data and exploiting a large-scale natural experiment, we estimate the effect of real-time usage information on residential electricity consumption in Northern Ireland. Starting in April 2002, the utility replaced prepayment meters with advanced meters that allow the consumer to track usage in real-time. We rely on this event, account for the endogeneity of price and payment plan with consumption through a plan selection correction term, and find that the provision of information is associated with a decline in electricity consumption of 11–17%. We find that the reduction is robust to different specifications, selection-bias correction methods and subsamples of the original data. The advanced metering program delivers reasonably cost-effective reductions in carbon dioxide emissions, even under the most conservative usage reduction scenarios.     

Development of short-rotation willow coppice systems for environmental purposes in Sweden

During the last three decades, driving forces behind the development of short-rotation willow coppice (SRWC) in Sweden have been changing from a primary focus on biomass production towards emphasis on environmental applications. In most cases, current commercial SRWC practice is geared towards a combination of biomass production for energy purposes and environmental goals. The latter goals range from decreasing the impact of specific contaminants in the environment to organic waste handling in a recycling system in urban and/or agricultural areas.Where biomass production and pollutant management overlap, the science of phytoremediation has its practical application. Through phytoremediation, waste products that previously have been a burden for the society can be used as valuable resources to increase short-rotation willow biomass production.In this paper we will present the terminology and definitions of different types of phytoremediation. We also give an overview of five different cases of phytoremediation activities with a potential for large-scale implementation. Some of the types of activities are already commercially used in Sweden; others seem promising but still need further development.     

The prospects of cost reductions in willow production in Sweden

The current and future costs of willow short rotation coppice production in Sweden are analysed, considering all relevant cost factors explicitly. The future production costs are estimated considering effects of coppice area expansion and learning. The current and future costs of land and of risk premiums are subsequently estimated. Subsidies for farmers are not considered. If the area of willow cultivation were to expand enough to generate economies of scale, the production cost could be cut by about 10% compared to the current level. When learning effects are also considered, the total cost reduction potential is about 35%. Two major cost components (fertilization and road transport) are roughly stable while two other major cost components (establishment and harvest) have larger prospects for cost reduction, primarily due to potential for learning. Land costs and risk premiums vary and are uncertain, but both are estimated to be potentially significant compared to other cost components. Requirements of risk premiums may become lower as a consequence of area expansion and learning. Land costs are subject to many factors that are inherently uncertain, not the least future food prices. Efficient policies promoting an expansion of willow cultivation are discussed.     

Sampling procedure in a willow plantation for estimation of moisture content

Heating value and fuel quality of wood is closely connected to moisture content. In this work the variation of moisture content (MC) of short rotation coppice (SRC) willow shoots is described for five clones during one harvesting season. Subsequently an appropriate sampling procedure minimising labour costs and sampling uncertainty is proposed, where the MC of a single stem section with the length of 10–50 cm corresponds to the mean shoot moisture content (MSMC) with a bias of maximum 11 g kg⁻¹. This bias can be reduced by selecting the stem section according to the particular clone. The average difference in MSMC between the largest and smallest shoot in a stump was 31 g kg⁻¹. This variation is only marginally smaller than the variation found in MC between stumps. The MC of individual stem sections may vary as much as 190 g kg⁻¹ in one shoot. Variation in whole shoot moisture content was primarily influenced by the shoot diameter, but in addition significant effects of clone and shoot age were found.     

The prospects for willow plantations for wastewater treatment in Sweden

The concept of willow vegetation filters for the treatment of nutrient-rich wastewater has the potential to address two of our most serious environmental problems today —water pollution and climate change— in a cost-efficient way. Despite several benefits, including high treatment efficiency, increased biomass yields, improved energy and resource efficiency, and cost savings, willow vegetation filters have so far only been implemented to a limited degree in Sweden. This is due to various kinds of barriers, which may be the result of current institutional, structural and technical/geographical conditions. This paper discusses the prospects of a more widespread utilisation of willow plantations for wastewater treatment in Sweden, including existing incentives and barriers, based on current knowledge and experience.     

生活垃圾与柳树枝共热解研究

在热重分析仪和固定床热解炉上进行柳树枝对生活垃圾热解特性影响研究,考察了柳树枝对生活垃圾热解失重率、热解活化能、热解产物产率、热解气组成的影响。热重分析结果表明,生活垃圾(M)、柳树枝(W)及生活垃圾和柳树枝混合物(MW)在265~600℃时失重最明显,当热解温度为600℃时,3种样品的失重率分别为61.41%,57.81%和70.31%;热解动力学分析表明,MW的热解活化能低于M和W,且低于MW理论活化能;固定床热解实验表明,当MW混合比例为4∶1时,热解产物理论值与实验值差距最大,M和W热解过程中存在明显协同作用;对MW热解气组成分析发现,随着W添加比例的增大,热解气体中CO_2产率下降,CH_4,H_2产率增加,当MW混合比例为4∶4时,CH_4和H_2产率分别提高1.13 m L/g和2.53 m L/g,CO_2产率降低1.68 m L/g。     

A simple technique for estimating above-ground biomass in short-rotation willow plantations

Successful purpose-grown willow production systems require regular monitoring of willow growth to apply timely management techniques for increased productivity and timing of harvest for maximizing profit. The objective of this study was to assess the efficacy of a novel method of estimating above-ground willow biomass, involving measuring light attenuation through the willow canopy, to calculate a ‘stem area index’ for relating to harvested willow biomass. Two different willow clones, with contrasting growth form, were used: single stem (Charlie) and multi-stem (SV1). Given the strong correlations (r² > 0.97; p < 0.05) between the measured stem area index and harvested willow biomass, regardless of growth form, it appears that this simple mensurative technique is a promising alternative for estimating above-ground biomass in short-rotation willow plantations.     

Interaction in Short Rotation Coppice willow,Salix viminalis genotype mixtures

Seven straight Salix viminalis genotypes with different levels of rust (Melampsora epitea) susceptibility were grown as mono-plots as well as being incorporated into a range of mixtures. Two 3-year harvests (2003 and 2006) were taken. Disease progress was followed on each of the individual genotypes throughout each growing season 2001–2006. In 2003 there were small but significant yield increases from the mixtures compared to the yield of individual components grown as mono-plots. These differences were not evident at the second harvest in 2006. No consistent effect of mixtures on reducing rust on the most susceptible genotype, Salix viminalis ‘77082’ were observed. In some years, e.g. 2003, at certain times during the growing season, significant reductions were observed on Salix viminalis ‘77082’ in certain 3-way mixtures compared to mono-plots. These, however, were not repeated consistently in subsequent years. It was concluded that the current commercial practice in many parts of Europe of planting mixtures as a disease control strategy will only be effective if there is sufficient genetic diversity between the Salix genotypes incorporated into the mixture.     

Long-term biomass productivity of willow bioenergy plantations maintained in southern Quebec,Canada

Maintaining the long-term productivity of short-rotation coppice plantations is very important to ensure the large-scale deployment of biomass as a renewable energy source. In Quebec (Canada), willow short rotation coppice has been studied since the early ‘90s, thereby allowing long-term analysis of the dynamic performance of several species and hybrids as well as management practices. In this study, we report on the long-term productivity of two trials maintained in southern Quebec and carried out to compare a) growth and biomass yield of willow Salix viminalis (cultivar 5027) grown for 15 years under fertilized and unfertilized conditions and b) growth of different willow cultivars over three successive rotations (10 years). The first trial showed that after four rotations, sludge-fertilized S. viminalis 5027 produced significantly more biomass, 19.2 odt ha⁻¹ yr⁻¹, whereas unfertilized plots yielded 13.8 odt ha⁻¹ yr⁻¹. The second trial showed that among the wide variety of commercial willow cultivars available, SX64 and SX61 along with some indigenous species (i.e. S25, S365, S546) were the most suitable for short-rotation forestry in southern Quebec.