Stanislavs Gendelis

Web-based real-time data acquisition system as tool for energy efficiency monitoring

A web-based data acquisition system is proposed as a research tool of the energy efficiency monitoring project of the test stands. Basic requirements for the architecture of the data acquisition system are discussed. The architecture of the data acquisition system is proposed to provide the real-time interface with sensors, to acquire and to log data from all sensors with fixed rate, and to deliver logged data through FTP to the end-user.

The Potential of Renewable Energy Sources in Latvia

Abstract The article discusses some aspects of the use of renewable energy sources in the climatic conditions prevailing in most of the territory of Latvia, with relatively low wind speeds and a small number of sunny days a year. The paper gives a brief description of the measurement equipment and technology to determine the parameters of the outer air; the results of the measurements are also analysed. On the basis of the data obtained during the last two years at the meteorological station at the Botanical Garden of the University of Latvia, the energy potential of solar radiation and wind was estimated. The values of the possible and the actual amount of produced energy were determined.

Impact of Different Building Materials on Summer Comfort in Low-Energy Buildings

Abstract The aim of the current paper is to analyse thermal comfort and overheating risks in the low-energy buildings in a summer season under Latvian climate conditions both experimentally and numerically. An interior temperature and relative humidity are analysed under free-floating conditions. Two cases are analysed: in one case, the solar influence through the window is taken into account; in the other this influence is omitted. Three different building solutions are observed: two building structures which mainly consist of the mineral wool and wooden materials and one structure from aerated clay bricks and mineral wool. The experiments have been implemented in test stands in Riga, Latvia. The numerical simulations based on measurements obtained from test stands have been performed using software WUFI Plus. The results show that the wooden constructions have high overheating risks.

Analyses of phase change materials’ efficiency in warm-summer humid continental climate conditions

The usage of phase change materials (PCMs) is a way to store excess energy produced during the hot time of the day and release it during the night thereby reducing the overheating problem. While, in Latvian climate conditions overheating is not a big issue in traditional buildings since it happens only a couple of weeks per year air conditioners must still be installed to maintain thermal comfort. The need for cooling in recently built office buildings with large window area can increase significantly. It is therefore of great interest if the thermal comfort conditions can be maintained by PCMs alone or with reduced maximum power of installed cooling systems. Our initial studies show that if the test building is well-insulated (necessary to reduce heat loss in winter), phase change material is not able to solidify fast enough during the relatively short night time. To further investigate the problem various experimental setups with two different phase change materials were installed in test buildings. Experimental results are compared with numerical modelling made in software COMSOL Multiphysics. The effectiveness of PCM using different situations is widely analysed.

Mathematical Modeling of Dual Layer Shell Type Recuperation System for Biogas Dehumidification

Abstract The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.