Giedrė Streckienė

Solar Assisted Ground Source Heat Pump Performance in Nearly Zero Energy Building in Baltic Countries

Abstract In near zero energy buildings (NZEB) built in Baltic countries, heat production systems meet the challenge of large share domestic hot water demand and high required heating capacity. Due to passive solar design, cooling demand in residential buildings also needs an assessment and solution. Heat pump systems are a widespread solution to reduce energy use. A combination of heat pump and solar thermal collectors helps to meet standard requirements and increases the share of renewable energy use in total energy balance of country. The presented paper describes a simulation study of solar assisted heat pump systems carried out in TRNSYS. The purpose of this simulation was to investigate how the performance of a solar assisted heat pump combination varies in near zero energy building. Results of three systems were compared to autonomous (independent) systems simulated performance. Different solar assisted heat pump design solutions with serial and parallel solar thermal collector connections to the heat pump loop were modelled and a passive cooling possibility was assessed. Simulations were performed for three Baltic countries: Lithuania, Latvia and Estonia.

A quantitative evaluation of theoretical renewable energy potential of the building site

AbstractModern building design process is becoming more complex. Local conditions and future constructions are computer-simulated. The aim of this simulation is to evaluate theoretical RE potential for the successful and efficient exploitation of the new building. As usual, in the simulation process of local conditions, the assessment of the renewable energy potential is one of the key elements. This article presents and analyses the idea of the quantitative evaluation of renewable energy (RE) theoretical potential of the building site and the approach on how to prepare initial data file for further process of site energy development concept creation. The study describes a building site that is undergoing the RE evaluation in terms of thermodynamic and descriptive statistics characteristics. The applicability of the offered approach was verified in the case study. The specified evaluation of the combined energy fluctuation throughout the year provides new and potentially crucial information about the issu...

EXPRESSING THE BUILDING ENERGY SYSTEMS THERMODYNAMIC SEASONAL EFFICIENCY

In order to reduce impact to environment, a qualitative approach of energy saving is global aspect that is included in various forms of CO 2 emissions, primary energy limitations and benchmarks in EU and member countries policy. Exergy analysis allows expressing the quality of energy flows in comparison to ambient or other reference conditions. Despite of this valuable information, this concept is not widely used in engineering practice. The article suggests the calculation procedure for sessional or periodical thermodynamic (exergy) efficiency in relation to variable reference conditions. Knowledge about defined procedures unlocks the possibility to fill up the implementation gap for building system engineering practice where seasonal performance parameters are widely used to express efficiency. Prepared algorithm allows determining seasonal or periodic thermodynamic efficiency of individual elements and energy transfer chains in building energy systems. Defined calculation procedure workflow is suitable for integrated approach when coupled heat transfer and fluid flow processes are explored in short time steps with dynamic simulation software tools. Presented algorithm ensures result that fits in thermodynamically correct range 0-1 and helps to summarize separate time step results. By adding duration of specific conditions, this analysis enables to identify critical peak periods and base load conditions across operation period. The presented framework fills the gap in lack of systematic expression for seasonal thermodynamic efficiency and suggests the process for calculation procedures workflow. DOI: https://doi.org/10.3846/enviro.2017.271

Analysis of seasonal exergy efficiency of an air handling unit

Ventilation systems play an important role for providing suitable indoor climate in buildings. Improving these systems allows promoting energy efficiency in building sector, which is responsible for a large percentage of global energy consumption. Therefore, this work focuses on assessment of ventilation air handling unit (AHU) using thermodynamics. The exergy analysis is used to evaluate the performance of an AHU. Special attention is made about seasonally varying exergy flows of a system. As efficiency of a ventilation system is closely linked to local climate, especially to the varying reference temperature. The paper presents an approach for calculating the seasonal exergy efficiency and gives the results of the AHU analysis. The case study reveals that the highest exergy consumption is when the outdoor temperature is −2.5 °C. The AHU case with heat recovery and water heater is the most efficient comparing to other cases investigated. The use of this methodology may be extended for determining of the ...