Carsten Bojesen

Choosing the Right Technology: Optimized Design of Renewable Supply Systems for Residential Houses

The use of renewable energy sources (RES) has continuously increased throughout the last decade. In the residential building sector the trend goes towards energy supply systems based on multiple RES. This is mainly due to political requirements, governmental subsidies and fuel price development. These systems not only require an optimal design with respect to the installed capacities but also the right choice in combining the available technologies assuring a cost-effective solution.

Local versus national: designing supply systems for individual net zero energy buildings with flexible electricity prices

The building sector has obtained increased awareness throughout the last decades due to its notable contribution to global greenhouse gas (GHG) emissions. One approach to decrease these emissions is the concept of net zero energy buildings (Net ZEB), which produce as much energy out of renewable sources as they consume through public grid connections on an annual balance. A global design solution for these buildings does not exist, since the energy resource availability is different everywhere. In earlier publications a methodology was presented which allows for the cost optimal design of individual energy supply systems based on on-site weather and building conditions, as well as considering the expected energy consumption profile. However, local planning processes are problematic if they do not take regional or national impacts into account. Given the grid connection, the local building solution also has an impact on a national scale by exchanging electricity. Therefore it is important to implement respective grid loads into the planning process in order to avoid technology choices, which might counteract grid stability or cost inefficiencies at other sites. The aim of this paper is to adapt the earlier proposed methodology by integrating flexible national electricity prices and thus taking account for the aforementioned effects. The methodology is applied in a case study for a single family house under Danish conditions. The results show that the system configuration might not necessarily be changed but an adaptation in the mode of operation is important and could even lead to cost reductions when allowing for flexible tariffs.

A flexible and low cost experimental stand for air source heat pump for Smart Buildings

Energy systems are faced with the challenges of reducing dependency on fossil fuels, while handling increasing penetration levels of intermittent renewables such as wind and solar power. At the same time, the efficient consumption of energy is vital for avoiding the impacts from increasing fuel prices. A significant part of this challenge may be dealt with in the way space heating, space cooling, and domestic hot water production which is provided to residential and commercial buildings. Air source heat pumps (ASHP) are widely used conversion technologies for providing building thermal energy services; cooling, heating, and water heating. ASHP does not have a constant temperature for the primary source like: soil, ground water, or surface water heat pumps. In result, laboratory experiments and tests are faced by the problem of having to handle a wide range of conditions under which the evaporator is operated. In order to cover various climate conditions, performance and behavior must be tested for temperatures ranging from -30°C to 40°C and for various humidity levels. This paper presents a state-of-art experimental stand, named controlled lab environment (CLE or climatic box), for testing ASHP under controlled evaporator ambient conditions. A main purpose of the CLE is to test and verify the performance and behavior of a theoretical model of the ASHP as a basis for optimization and efficiency improvements. Together with thermal storage technologies and intelligent control system this technology may come to play a key role in the development of Smart Buildings in future energy systems. While experimental results are not yet available the paper presents the design considerations and schematics of the CLE. Furthermore, a thermodynamic model of an ASHP is presented.

Air source heat pump a key role in the development of smart buildings in future energy systems: Low cost and flexible experimental setup for air source heat pumps

An important challenge for energy systems today is reducing dependency on fossil fuels, while handling increasing penetration levels of intermittent renew abies such as wind and solar power. The efficient consumption of energy is a vital mater for a sustainable energy system. A significant part of energy is used for space heating, space cooling, and domestic hot water production which are provided to residential and commercial buildings. Air source heat pumps (ASHP) are widely used conversion technologies all over the world for providing building thermal energy services as: cooling, heating, and water heating. ASHP does not have a constant temperature for the primary source like: soil, ground water, or surface water heat pumps but still have a majority in usage. As result, laboratory experiments and tests are faced by the problem of having to handle a wide range of conditions under which the evaporator is operated. In order to cover various climate conditions, the performance and behavior of the ASHP must be tested for temperatures ranging from -30°C to 40°C and for various humidity levels. This paper presents an experimental stand, named controlled lab environment (CLE or climatic box), for testing ASHP under controlled evaporator ambient conditions. A main purpose of the CLE is to test and verify the performance and behavior of a theoretical model of the ASHP as a basis for optimization and efficiency improvements. Design considerations and schematics of the CLE are presented. Furthermore, a thermodynamic model of an ASHP is presented and simulation results.

Modelling of hot water storage tank for electric grid integration and demand response control

District heating (DH), based on electric boilers, when integrated into electric network has potential of flexible load with direct/indirect storage to increase the dynamic stability of the grid in terms of power production and consumption with wind and solar. The two different models of electric boilers for grid integration are investigated: single mass model (with uniform temperature inside tank) and two mass model (with ideal single stratified layers). In order to investigate the influence of demand response and grid voltage quality with the measurable parameter of electrical boiler in practice, selection of a proper model is equally important. The results obtained from comparison of two models (when input to the model is thermal energy demand) are present with their significance and advantages for grid integration and demand response. Models mathematics are shown in detail with the validation of result.

A custom flexible experimental setup to test air source heat pump for smart buildings

In this paper a custom made experimental stand is presented, named controlled lab environment (CLE or climatic box), built for testing an air source heat pump (ASHP) under controlled evaporator ambient conditions and verify the performance and behavior of a theoretical model of the ASHP as a basis for optimization and efficiency improvements. While the data acquisitions from experiments are not yet available, the paper presents the design considerations and schematics of the CLE and a thermodynamic model of an ASHP.