Category Archives: Science

New Paper on HVAC: Ventilation Control in a School Building

Data-Driven Occupancy Profile Identification and Application to the Ventilation Schedule in a School Building

Available with open access at https://www.mdpi.com/1996-1073/17/13/3080

Abstract: Facing the current sustainability challenges requires reduction in building stock energy usage towards achieving the European Green Deal targets. This can be accomplished by adopting techniques such as fault detection and diagnosis and efficiency optimization. Taking an Estonian school as a case study, an occupancy-based algorithm for scheduling ventilation operations in buildings is here developed starting only from energy use data. The aim is optimizing the system’s operation according to occupancy profiles while maintaining a comfortable indoor climate. By relying only on electricity meters without using carbon dioxide or occupancy sensors, we use the historical data of a school to develop a DBSCAN-based clustering algorithm that generates consumption profiles. A novel occupancy estimation algorithm, based on threshold and time-series methods, then creates 12 occupancy schedules that are either based on classical detection with an on-off method or on occupancy estimation for demand-controlled ventilation. We find that the latter replaces the 60% capacity of current on-off schedules by 30% or even 0%, with energy savings ranging from 3.5%
to 66.4%. The corresponding costs are reduced from 18.1% up to 62.6%, while still complying with current national regulations for indoor air quality. Remarkably, our method can immediately be extended to other countries, as it relies only on occupancy schedules that ignore weather and other location-specific factors.

A guest lecture on classical mechanics

Here is a guest lecture I have done last March at Aalto University for the course “Stability of Structures”, which was lectured by my late friend and inspirational figure Dr. Djebar Baroudi.

https://www.dropbox.com/scl/fi/k1kra0ojyhjxe1dwvp1c2/Lagrangian-mechanics.pdf?rlkey=ea0wlboqe1llhiauca3xnrpxm&dl=0

Title: “Lagrangian and Hamiltonian mechanics: formal aspects and engineering applications”

TOPICS:

PART I: FORMALISM

1.From Newtonian to Lagrangian Mechanics

2.The Lagrangian function

3.Generalized Coordinates, Momenta, and Forces

4.Hamilton Principle and Lagrange Equations

5.Hamilton equations and cyclic coordinates

6.Symmetry and Conservation Laws

7.Constraints and Friction Forces

8.Calculus of Variations and Lagrange Multipliers

9.Canonical Transformations and Hamilton-Jacobi Equations

PART II: APPLICATIONS

1.Fluid Mechanics

2.Chaos and Non-Linear Dynamics, including Bifurcations

3.Buckling of compressed elastic structures (nonlinear instability)

4.Structural collapse simulations

5.Aeronautical Engineering

6.Constructing Quantum Mechanics

7.Quantum Field Theory and Particle Interactions

8.General Relativity and Einstein Equations

9.Cosmology and Dark Matter

New publication on energy storage

This paper investigates how a simulated room’s energy and temperature performance are affected if its underfloor heating control is modelled with increasing detail. Experiments were performed to develop and calibrate an empirical model of wax motor and to calibrate the valve curve. These models were used to implement and test the On/Off and proportional-integral (PI) control processes at various levels of modelling detail. Controllers were implemented by gradually adding optimized control parameters, signal delay, calibrated valve curve, signal modulation, and actuator modelling. The On/Off control dead band and PI parameters exhibited the largest impact, reducing energy use (1%–5%) and temperature fluctuations (ca 1 K). Modulating the PI output signal increased temperature fluctuations to the same amplitude as On/Off with 0.5 K dead band, increasing space heating demand by 1.3%. The wax actuator counted for less than 1%; however, it increased time delays to maximally 7 min and remarkably changed the mass flows.

Parts , T M , Ferrantelli , A , Naar , H , Thalfeldt , M & Kurnitski , J 2023 , ‘ Wax actuator’s empirical model development and application to underfloor heating control with varying complexity of controller modelling detail ‘ , JOURNAL OF BUILDING PERFORMANCE SIMULATION . https://doi.org/10.1080/19401493.2023.2201818

New paper on energy data mining now published

Office Building Tenants’ Electricity Use Model for Building Performance Simulations
https://www.mdpi.com/1996-1073/13/21/5541

Abstract

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 simulationoffice buildingsenergy performanceenergy modellingHVACanalytical modellingstatistical analysis

New paper on geothermal energy published

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:
https://www.sciencedirect.com/science/article/pii/S037877882031152X?dgcid=author

Abstract

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.

New paper published: “A novel method for calculating heat emitter and controller configuration setpoint variations with EN15316-2”.

We published a new article! Highlights of the paper, available at https://doi.org/10.1016/j.jobe.2020.101387:

  • A novel method for the accurate calculation of total setpoint variations.
  • Effects of real system losses are better represented than with component assessment
  • Simulations of annual energy consumption compare losses for new and old building.
  • A common platform to compare emission efficiency under standardised conditions.

Abstract:
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%.

Special Issue “Energy Performance and Indoor Climate Analysis in Buildings” available for free download

Our Special Issue with MDPI titled “Energy Performance and Indoor Climate Analysis in Buildings” (18 papers) is available for free download here: https://www.mdpi.com/books/pdfview/book/1828
#Engineering #energy #Sustainability #Science #civilengineering

Special Issue “Energy and Technical Building Systems – Scientific and Technological Advances” now published

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