Institute of Energy Systems and Environment

Energy efficiency of buildings has become a significant issue in Latvia and across Europe. More than a half (by heated area) of Latvian housing stock consists of multi-family buildings. 63% of buildings are panel houses built during the Soviet era when no one thought about energy efficiency issue and energy resources was very cheap. Today, energy prices are increasing, the EU sets targets to increase energy efficiency, reduce of GHG emissions and promote the use of renewables. Building renovation is a sustainable approach for Latvia to achieve these objectives because the housing sector is a huge consumer of energy-40% of total energy consumption. A great way to promote such renovations is to use Energy Performance Contracting (EPC) concept. EPC is a legal contract between the beneficiary and the provider (an ESCO) of an energy efficiency improvement measure, verified and monitored during the whole term of the contract, where investments (works, supplies or services) in that measure are paid for in relation to a contractually agreed level of energy efficiency improvement. In Latvia, EPC+ contracting has been recently applied to the comprehensive renovation of multi-family residential buildings. A study is being carried out on 12 projects, which have been implemented over the last 5 years. Measurements and calculations have been carried out. Based on 2013 data, on average space heating consumption of fully completed buildings is down to 77 kWh/(m 2 a) and network circulation losses is down to 4.5 kWh/(m 2 a), meaning a combined figure of 81.5 kWh/(m 2 a). The energy savings of the renovated building stock are calculated at 55%. On average space heating consumption of buildings partly completed is expected to be down to 72 kWh/(m 2 a) and network circulation losses down to 2.4 kWh/(m 2 a), meaning a combined figure of 74.4 kWh/(m 2 a). The energy savings of the renovated building stock are calculated at 65%.

Small-Scale Cogeneration Plant Data Processing and Analysis In the article, the operational data on electricity and heat energy generation in a small-scale cogeneration plant are analysed. Different measurements done in the plant formed a basis for estimation and evaluation of the savings of primary energy in comparison with distributed energy production. The authors analyse the efficiency values for the heat and the electricity production in the cogeneration regime and the savings of primary energy when the cogeneration plant works with partial load.

The EIA procedure in Latvia as it`s known today was implemented by the law „On environmental impact assessment” in 1998. The quantity assessment of expected environmental impact is provided by indicators giving the highest impartiality in this process. The choice of indicators and their approval in EIA projects in Latvia have not received the right attention, the issue is left upon the EIA performers. The problematic issues on necessity of indicator selection and validation are dealt with in the article. 39 environmental indicators were selected for EIA of motor road projects, with the evaluation of their significance and essence, as well as the analysis f application of these indicators in 14 reports concerning EIA of motor road projects. The results revealed the existing problems of indicator application and proved the assumption that there is no common indicator system for the assessment of impact of similar economic projects, proving the necessity of indicator validation to ensu...

Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM's suitability for certain applications.

Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM’s suitability for certain applications.

One of the main pollution types is air pollution, which has a significant impact on the surrounding environment and on living beings. Major source of air pollution is combustion processes. There are many flue gas treatment technologies around the world. In this paper a new, innovative flue gas treatment technology – fog unit – is introduced. The goal of the fog unit is to treat flue gases that are emitted from households. In the European Union, including Latvia, at the beginning of 2020, a directive will come into effect that will set limits for emissions and the effectiveness for incinerators in households. The main focus of this study was to determine the most optimal operating mode for the fog unit by changing different operating parameters: sprayed water temperature, sprayed water flowrate and types of nozzles (drop diameters). Results show that the most optimal operating mode in terms of flue gas treatment efficiency and recovered energy is at water temperature: 20 °C, sprayed ...

The research on solar heating systems often is faced with choice of carrying out experiments in real systems with changing parameters or to use modelling software with constant parameters but many undefined parameters or assumptions. The design of experimental system for simulating solar heat accumulation is proposed in this paper. The proposed design allows testing of phase change materials which provide higher thermal density compared to water. Results from computational fluid dynamic simulations carried out by other studies have been analysed for implementation into designing of the tank. All of these factors have been taken into account to create a system that resembles real case and can simulate for a long periods of time.

The use of biofuels for heating purposes is beneficial from a greenhouse gas emission point of view. But combustion of solid biofuels typically is related with high emission rates of CO, NOx, PAHs, VOCs and particle matter. The most important factor that is affecting the formation of harmful emissions is the way the combustion process is organised. The amount of air injected and approach for the air supply system, are the most important factors affecting combustion process. Air staging is one of the most effective technical solutions for achieving complete combustion and low emissions. The main idea of air staging is to inject air into different zones of a combustion process. The main goal of this study is to optimise pellet combustion process in a 500 kW boiler with staged air supply. The research is based on on-site experiments and application of scientific instrumentation. Fly- away unburned fuel particles were discovered during the on-site experiments. Reduction of the amount of...

With the increase of renewable energy sources, the control methods of the energy systems are an increasingly important topic. Control methods have evolved from simple on/off controllers to methods that utilize artificial intelligence and can have a predictive nature. This paper investigates the control methods that are particular for solar thermal systems. A bibliometric method is applied to analyse scientific literature related to the specific application from the Web of Science database. Results show that recent developments in control methods focus on solar thermal to power and hybrid systems while district heating is a potential research gap. Annual publication trends, country, journal and keyword analysis is presented.

Mathematical model has been developed to assess the effects of using phase change materials (PCM) in a fully mixed water accumulation tank. Packed bed system of spheres with a diameter of 40 mm have been considered as an option to increase energy storage density. A continuous phase model has been applied to analyse the influence of phase change during a charging and discharging processes. The methodology for calculating energy mass flow, density of water, heat transfer between layers, temperature for each time step and energy transferred to PCM is given. Single type of PCM with melting temperature of 55 °C and multiple type PCM system (65, 55, 45 and 35 °C) are compared. It is found that multiple type PCM system compared to only water and single type PCM systems, provide lower return temperatures and higher energy density.

Commercially, furfural is produced from pentosan-rich biomass using mineral acids, such as H2SO4 and H3PO4, as a homogeneous catalyst. In this study, environmentally friendly Al2(SO4)3 was used for the conversion of hemicelluloses to furfural by hydrothermal pretreatment in a continuous steam flow reactor. Hemp (Cannabis sativa L.) shives were used as a feedstock due to the high content of hemicelluloses (30.2 wt%) – and the use of hemp shives has not been investigated for furfural production to date. In this study, the variable treatment parameters were residence time (10-90 min), temperature (140-180ºC) and the amount of the catalyst (3-7 wt%). The highest obtained yield of furfural was 71.1% of the theoretical yield.

h i g h l i g h t s " The improvements for the performance of the pellet boiler. " Ratio of the supplied combustion air in polynomial order affects CO emission and efficiency. " The location of the intake point for combustion air influences the thermal losses.

In this paper the possibility to reduce CO 2 emissions by energy recovery from waste tyres is discussed. The objective of the study is to analyze the end-of-life tyre market in Latvia, to assess the amount of used tyres available and to calculate the potential reduction of CO 2 emissions by energy recovery from tyres in mineral products industry. Calculation results show that an improved collection and combustion of end-of-life tyres in the cement industry can save up to 17% of the present CO 2 emissions in the mineral products industry.