Submissions are welcome for the new Special Issue at Energies MDPI where I am guest editor.
Deadline: April, 27th 2022. https://www.mdpi.com/…/Building_Sustainable_District
Office Building Tenants’ Electricity Use Model for Building Performance Simulations
Large office buildings are responsible for a substantial portion of energy consumption in urban districts. However, thorough assessments regarding the Nordic countries are still lacking. In this paper we analyse the largest dataset to date for a Nordic office building, by considering a case study located in Stockholm, Sweden, that is occupied by nearly a thousand employees. Distinguishing the lighting and occupants’ appliances energy use from heating and cooling, we can estimate the impact of occupancy without any schedule data. A standard frequentist analysis is compared with Bayesian inference, and the according regression formulas are listed in tables that are easy to implement into building performance simulations (BPS). Monthly as well as seasonal correlations are addressed, showing the critical importance of occupancy. A simple method, grounded on the power drain measurements aimed at generating boundary conditions for the BPS, is also introduced; it shows how, for this type of data and number of occupants, no more complexities are needed in order to obtain reliable predictions. For an average year, we overestimate the measured cumulative consumption by only 4.7%. The model can be easily generalised to a variety of datasets.
Keywords: building simulation; office buildings; energy performance; energy modelling; HVAC; analytical modelling; statistical analysis
Our latest paper introduces a tabulated tool that aids in the early design of geothermal systems, by providing estimates of the system’s efficiency according to the chosen energy piles field configuration and heat pump sizing.
Direct link: https://doi.org/10.1016/j.enbuild.2020.110178
The paper can be downloaded FOR FREE for 50 days at this link:
Geothermal systems are often employed for both the heating and cooling of sustainable constructions. Energy piles (U-shaped heat exchangers inserted into the foundation piles) are widely included in these installations, whose performance is usually estimated by means of complex, time-consuming simulations already at an early design stage.
Here we propose a simple methodology, where a hand calculation tool provides the condenser yield per pile meter, ground area yield and demand covered by the heat pump by specifying only building heat load and geometric characteristics of the energy piles field. Our tool is tested by assuming 20 years of operation in a hall-type commercial building in a cold climate. A validated IDA-ICE parametric study couples the heat pump evaporator operation with heat transfer processes between energy piles and soil. Various system configurations are considered and thermal storage in the soil is included.
We find that the expected yield is not directly proportional to pile separation, while a smaller extraction power is favoured. Thermal storage in the soil is also confirmed to be critical. Besides our specific quantitative results, our practical guideline is qualitatively general and can be extended to any given building type and climate.
We published a new article! Highlights of the paper, available at https://doi.org/10.1016/j.jobe.2020.101387:
Estimating heat emission losses of heating systems is an important task of energy efficiency assessments in buildings. However, the present international standards do not specify how emission losses should be calculated or measured for different emitter and control system configurations. Aiming to fill this gap, here we propose a method for computing the temperature setpoint variations by addressing the heat distribution throughout a room with space heat emitters. This general and exact procedure enables the calculation of product category-specific setpoint variations for different types of heat emitters, accounting for the overall heat balance in the enclosure and including the cross-correlations of each component. Our method complements the procedure presented in the Standard EN15316-2, making it possible to compute emission losses as product-specific values of setpoint variations instead of tabulated values. As the main finding of the study, the calculation process is defined for a European Reference Room that allows an accurate and transparent evaluation of total setpoint variations. These are computed for specific products from measured vertical stratification and control parameters, by means of an annual IDA ICE simulation model of the reference enclosure. Applying the method to an annual energy performance simulation for an old and a new building in Strasbourg shows that emission losses are compensated by a total setpoint variation of respectively up to 2.00 °C and 1.20 °C, corresponding to an increase in total heating energy usage of up to 22% and 20%.
Our special issue with @MDPIOpenAccess “Energy and Technical Building Systems – Scientific and Technological Advances” (10 papers published) is now fully and freely available in pdf at https://www.mdpi.com/journal/energies/special_issues/energy_and_built_environment #Engineering #energy #energyefficiency #Sustainability #HVAC
Sector coupling is a concept referring to the electrification of end-use sectors (e.g. heating and transport); it aims at increasing the share of renewable energy (solar, hydro, geothermal, wind, bioenergy, waste heat…) in these sectors.
In practice, this is a strategy “to provide greater flexibility to the energy system so that decarbonisation can be achieved in a more cost-effective way”.
The EU has committed under the Paris Agreement to make an effort to keep the global temperature rise below 2ºC, and the decarbonisation of the energy system can be crucial to this purpose. Sector coupling then becomes a key player for the EU “policy objective of shifting from our current highly centralised and mainly fossil fuel-based energy system to a more decentralised, energy efficient and renewable energy-based energy system”.
The quoted paragraphs are taken from an official European Parliament document on Sector Coupling, which you can find at the link below. I strongly encourage everybody interested in energy systems to read it (especially those who are critical towards the usage of wind and solar energy…yes, they still do exist!).
A short and coincise presentation I gave in Trondheim (Norway) on 7.11.19, which summarizes the parametric study reported in the conference paper (see the link below).
Here you can download the pdf (open access):
I will give the talk next week at the 1st Nordic nZEB+ conference in Trondheim, Norway!
Geothermal energy constitutes an important renewable resource that will become increasingly prominent in future constructions. A common method of extraction and usage consists of installing, inside the foundation piles of buildings, U-shaped heat exchangers called ”energy piles”.
In this paper such installations are addressed by means of a full parametric study, performed for a hall-type commercial building in a cold climate. By computing the transient heat transfer between energy piles and ground for a period of 20 years, guidelines for a preliminary sizing of the geothermal system as a whole are provided. These are valid for this specific building and climate, for a clay-type soil and without assuming thermal storage.
A highly nonlinear behaviour of the expected yield in relation to pile separation and evaporator extraction power is observed. Furthermore, 15m-long piles are found to be more efficient than those with double length, a smaller extraction power seems to be more favourable and differences in the pile diameter have little impact for heat transfer. A geothermal system sizing guide, which is useful for a preliminary quantitative test prior to any installation, is introduced. Even though our specific results are valid only for a commercial hall-type building in Finland, our procedure is qualitatively general and can be utilized for any given building type and climate zone.
Following the Taoist aim at simplicity, I have redesigned the website with a simpler layout, and cleared up all the pages from redundancies.
Hopefully now everything is more accessible, go and have a look!