Thermal Energy Services Research Articles

The GENEAP project: digitalising and automating planning of district heating and cooling

The Swiss Energy Strategy 2050 implies a transformation of the provision of thermal energy services (heating and cooling) to become CO2 neutral, district heating and cooling (DHC) are an important solution, which is technically challenging to design and whose implementation entails certain risks for investment. The GENEAP (Geospatial Analysis and Planning) project developed a software that applies automation and digitalisation to address this barrier and to apply scientific research to support the work of practitioners. The software Thermal Energy System Simulation Assistant (TESSA) increases reproducibility and decreases errors, and thereby reducing overall costs. We introduced innovative algorithms for modelling heat and cooling demand, thermal energy supplies, and the cost of thermal network technologies under different retrofit and climate change scenarios. We developed graph theory-based algorithms for computationally efficient routing of thermal network pipes. The goal of the GENEAP project was to validate the models and to establish how practitioners would find value in such a tool. Through workshops and interviews we established the need for digital tools due to the rapidly increasing need for new projects, the complexity and long time frames of projects, and the limited number of available experts to do this work. We found a gap between the high level energy strategy (Plan Directeur Energetique) and the detailed engineering design stage. In between these two stages we find the need for a flexible approach that can integrate cities and societies needs into the engineering design with non-energy requirements (e.g. political context, urban constraints and opportunities, etc).

Tackling thermal integration in the synthesis of polygeneration systems for buildings

A novel methodology is proposed for the synthesis of polygeneration systems in tertiary sector buildings with detailed thermal integration. The methodology involves a systematic approach that combines Pinch Analysis, mathematical programming, and the definition of a superstructure with thermal flexibility whereby mass flows can exchange heat in various temperature intervals. With the detailed characterization of the thermal energy flows associated with the thermal energy technologies and services to be supplied to the building, the optimization procedure provides a more realistic system configuration, ensures that thermodynamic principles are satisfied, and allows for synergies and potential benefits to emerge. The methodology is first introduced through a simple example of a gas engine-based energy system, highlighting the necessity of a detailed characterization of the hot and cold flows regarding their quantity and quality levels. Then, the approach is applied to the case study of a Brazilian university hospital that requires electricity, steam, hot water, and chilled water. The optimization is formulated as a multi-period mixed integer linear programming model that minimizes the total annual cost of installing and operating the system using local-based data. The results show the technical and economic interest of deploying cogeneration gas engines to cover electricity and thermal energy services. Besides, a strong synergy is observed between the cogeneration gas engine and the single-effect absorption chiller. Thus, it is demonstrated how a preliminary analysis of thermal integration opportunities must be an integral part of the optimal synthesis of energy supply systems.

Assessment of decarbonisation scenarios for the residential buildings of Serbia

Thermal energy demand in the residential building sector represents a big challenge for Serbia. In order to understand how to reduce this demand, and thereby avoiding GHG gas emissions, a bottom-up simulation model was developed. The model built the business-as-usual and two decarbonization scenarios up to 2030. For each scenario, such results as useful and final energy consumption, associated CO2 emissions, energy costs, investment costs and others were prepared at each level of the building stock segmentation. To develop such a detailed model, the topology of the residential building stock was developed and used as an input. For each individual building type, three retrofit packages of different stringency were analyzed. The paper delivers several important messages for the decarbonization of Serbia. First, it argues that the level of thermal energy services consumed by Serbian households is inadequate to address their needs. Second, the households of Serbia are likely to consume more wood than it was reported by national energy balances. Third, thermal energy efficiency retrofits can significantly reduce household energy demand at the same time as offering higher thermal comfort. However, the required investments are high and therefore benefits beyond energy cost savings should also be considered in order to make the transition to the low energy building stock economically feasible. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/TSCI181228017E">10.2298/TSCI181228017E</a><u></b></font>

Performance and profitability perspectives of a CO2 based district energy network in Geneva's City Centre

A new type of district energy network providing simultaneously heating and cooling services is being investigated. It is based on the use of CO2 as a heat transfer fluid by taking advantage of the latent heat of vaporization, to store and transfer heat across the network. The goal of the present study is to determine the performance of a CO2 network when applied to a real urban area. It focuses first on determining the requirements for the various thermal energy services for a part of Geneva's City Centre. The final energy consumption is first computed for the energy conversion technologies now in place in this area – namely heating oil boilers and air cooled compression chillers. Then the new final energy consumption is computed considering that a CO2 network is used instead of boilers and air cooled compression chillers. For the area considered the CO2 network's variant leads to a final energy consumption of 10,968 MWh of electricity. It represents a reduction of 84.4% when compared to the boilers and chillers case. A comparative profitability analysis of the two cases is also presented. The analysis takes into account investment, heating oil and/or electricity, equipment replacement, operation, and maintenance costs, as well as the sales of energy services.For an interest rate of 6%, a price of the delivered heating/cooling services at 0.108 € kW h−1 and a lifetime of 40 years, the conventional technology does not reach profitability while the CO2 network achieves a profit in present value of 69.59 million € and the break-even point is reached after 5.5 years of operation.

Incorporating the user perspective into a proposed model for assessing success of SHS implementations

Modern energy can contribute to development in multiple ways while approximately 20% of world's populations do not yet have access to electricity. Solar Home Systems (SHSs) consists of a PV module, a charge controller and a battery supply in the range of 100 Wh/d in Sunbelt countries. The question addressed in this paper is how SHS users approach success of their systems and how these user's views can be integrated in to an existing model of success. Information was obtained on the user's approach to their SHSs by participatory observation, interviews with users and by self-observation undertaken by the lead author while residing under SHS electricity supply conditions. It was found that success of SHSs from the users' point of view is related to the ability of these systems to reduce the burdens of supplying energy services to homesteads. SHSs can alleviate some energy supply burdens, and they can improve living conditions by enabling communication on multiple levels and by addressing convenience and safety concerns. However, SHSs do not contribute to the energy services which are indispensable for survival, nor to the thermal energy services required and desired in dwellings of Sunbelt countries. The elements of three of the four components of our previously proposed model of success have been verified and found to be appropriate, namely the user's self-set goals, their importance and SHSs' success factors. The locally appropriate, and scientifically satisfactory, measurement of the level of achievement of self-set goals, the fourth component of our model of success, remains an interesting area for future research.

Mapping demand for residential building thermal energy services using airborne LiDAR

Within the urban environment the building sector typically accounts for around half of the total energy used, with the majority of this demand driven by thermal services including hot water and space conditioning. Accurately quantifying and locating building energy demand is essential to aiding energy management and planning initiatives across the city. However, a shortage of techniques that enable the effective scaling of individual building energy models to larger areas is evident. To help meet this need, we present a novel approach that utilizes airborne Light Detection and Ranging (LiDAR) data to populate a range of residential building energy and urban form parameters, including envelope resistivity, air leakage and solar gains. These parameters are then integrated with additional spatial datasets and allow for the calculation of baseline estimates of energy demand for contiguous regions within urban areas. We illustrate the outcomes of the model by predicting energy demand across a mixed residential neighbourhood in the City of Vancouver, Canada. Results indicate that the annual estimates of thermal energy demand closely match those derived from building energy simulation software (R2=0.93, p<0.001), while monthly estimates of demand show no statistically significant differences between our results and those from the simulation software (t=−0.11, p=0.91).