Do-a-thon: Collect approaches to thermal energy systems

zurich-2018
do-a-thon

#1

The question of how to adequately model thermal energy systems has been raised in several contexts:

Collecting the threads that were discussed before, I would like to discuss that issue on the upcoming workshop. It seems that quite some people are dealing with thermal systems, which I think could make a joint meeting very fruitful.

My suggestion would be to discuss the current approaches to model different components. As many of us seem to use LP/MILP models, i.e.:

  • CHP
    Different types and features: Backpressure, Extraction Turbine, minimum load, non-constant efficiency,…

  • Heat pumps
    Features: Temperature dependent COP
    Questions: How do people handle the distinction between air, ground and water HP?

  • Thermal storages
    Commonly used are simple capacity models.
    Are there any more detailed stratified models known?

  • District heating networks
    Accounting for thermal losses and pumping power

  • Solar thermal plants

As thermal systems feature nonlinearities when explicitly accounting for temperature levels, the linear modeling approach might not be sufficient for all purposes. In some cases, coupling to a nonlinear simulation model can be a solution. Many projects use tools like TRNSYS, EBSILON to calculate steady state or dynamic behaviour.

However, these tools are not free. Therefore, I suggest a discussion on how to approach these topics. Sharing our experiences in using open models in the heat sector could lead to a collection the features and the limitations of the current tools and ideas for new developments.


#2

I am interested and will participate. Maybe I can also offer some preliminary results of our current project!


#3

Were there any notes produced?


#4

Approach to thermal energy systems

Modeling specific technologies:

  • Overview of technologies:

[1] Power-to-heat for renewable energy integration: A review of technologies,

modeling approaches, and flexibility potentials, Andreas Bloess, Wolf-Peter Schill, Alexander Zerrahn

  • CHP

Oemof uses the approach of Mollenhauer2016

http://oemof.readthedocs.io/en/features-docu-improvements-jnnr/oemof_solph.html#genericchp-component

Backpressure, Extraction Turbine, minimum load, non-constant efficiency, flue gas losses, cooling water

[1] E. Mollenhauer, A. Christidis, and G. Tsatsaronis, “Evaluation of an energy- and exergy-based generic modeling approach of combined heat and power plants,” Int. J. Energy Environ. Eng., vol. 7, no. 2, pp. 167–176, 2016.

Bryn Pickering pointed at this paper:

[2] D. Faille, C. Mondon, and B. Al-Nasrawi, “mCHP optimization by dynamic programming and mixed integer linear programming,” Proc. 14th …, pp. 572–577, 2007.

[3] Dispa-SET uses this approach:

  • Kavvadias, K., Hidalgo Gonzalez, I., Zucker, A. and Quoilin, S., Integrated modelling of future EU power and heat systems: The Dispa-SET v2.2 open-source model, JRC Technical Report, EU Commission, 2018

  • relation between temperature and slope

  • JP J. Navarro, KC. Kavvadias, S Quoilin, A Zucker, The joint effect of centralised cogeneration plants and thermal storage on the efficiency and cost of the power system, Energy, Volume 149, 2018, Pages 535-549, https://doi.org/10.1016/j.energy.2018.02.025.

  • Heat pumps

Features: Temperature dependent COP

Questions: How do people handle the distinction between air, ground and water HP?

Also on larger level temperature might be important to consider and make a difference.

https://www.sciencedirect.com/science/article/pii/S0360544216304352?via%3Dihub

[1] I. Staffell, D. Brett, N. Brandon, and A. Hawkes, “A review of domestic heat pumps,” Energy Environ. Sci., vol. 5, no. 11, p. 9291, 2012.

[2] Integration of large-scale heat pumps in the district heating systems of Greater Copenhagen. Bjarne Bach, Jesper Werling, Torben Ommen, Marie Münster, Juan M. Morales, Brian Elmegaard, Energy, Volume 107, 2016, Pages 321-334, ISSN 0360-5442, https://doi.org/10.1016/j.energy.2016.04.029.

-> “No significant impact was found when comparing fixed and varying operation characteristics of the HP.”

CONSOCLIM model:

  • Thermal storages

Commonly used are simple capacity models.

Are there any more detailed stratified models known?

MILP-Implementation:

[1] T. Schütz, R. Streblow, and D. Müller, “A comparison of thermal energy storage models for building energy system optimization,” Energy Build., vol. 93, pp. 23–31, 2015.

Simulation models:

[2]

M.-S. Shin, H.-S. Kim, D.-S. Jang, S.-N. Lee, Y.-S. Lee, and H.-G. Yoon, “Numerical and experimental study on the design of a stratified thermal storage system,” Applied Thermal Engineering , vol. 24, no. 1, pp. 17–27, 2004.

[3]

E. M. Kleinbach, W. A. Beckman, and S. A. Klein, “Performance study of one-dimensional models for stratified thermal storage tanks,” Solar energy , vol. 50, no. 2, pp. 155–166, 1993.

[4]

A. M. Hafez, M. A. Kassem, and O. A. Huzayyin, “Smart adaptive model for dynamic simulation of horizontal thermally stratified storage tanks,” Energy , vol. 142, pp. 782–792, 2018.

Different modelling approaches (Non-linear):

[5]

Hot water tanks: How to select the optimal modelling approach?

O Dumont, C Carmo, R Dickes, E Georges, S Quoilin, V Lemort

  • District heating networks

Accounting for thermal losses and pumping power

How does the behaviour depend on the temperature levels?

Modesto library:

https://www.researchgate.net/publication/324834672_Modesto_-_a_multi-objective_district_energy_systems_toolbox_for_optimization

  • Solar thermal plants

SolarGrids

Models that determine steady state or dynamic behaviour (alternatives to TRNSYS etc.)

https://github.com/oemof/tespy http://tespy.readthedocs.io/en/master/

Wiki for approaches with several detail levels --> could be hosted on oemof_heat project github site

  • detailled process simulation

  • shortcut model (non linear, but not as detailled as the detailled simulation)

  • linearized approach

Approaches for nonlinear optimsation


#5

This is true only for water based HP, as the second paragraph in the Conclusions says:

The seasonal variation in COP is, however, not found to have a significant impact on the overall result. This is mainly because the COPs of water based heat pumps do not vary significantly throughout the year.

and in the Discussion:

For investigations involving air source heat pumps, modelling with an hourly COP, could on the other hand, be relevant.


#7

Hey, cool summary. Is there a simple way to understand 9c, e.g. why is the denominator a quadratic function of T_t^2 and is there a valid temperature range given?


#8

Thanks for pointing this out. Do you have any literature concerning the (LP/MIP) modelling of air source heat pumps?


#9

The equation part comes from the consoclim model and was provided by squoilin. @squoilin: Do you have a reference for those equations?


#10

No, I’m sorry about that.