The role of thermal storage and natural gas in a smart energy system

TLDR: In this paper, the authors highlight the economic importance of the thermal storage tank, which requires a thermal capacity of two to three times the hourly thermal power output of the CHP to optimize electric power production and limit thermal losses.

Abstract: Smart grids are considered important building blocks of a future energy system that facilitates integration of massive distributed energy resources like gas-fired cogeneration (CHP). The latter produces thermal and electric power together and as such reinforces the interaction between the gas and electricity-distribution systems. Thermal storage makes up the key-source of flexibility that allows decoupling the electricity production from the heat demand. However, smart grids focus on electricity, often disregarding the role of gas and thermal storage in overall smart energy systems. We find that the technical impact of a massive introduction of CHP on the gas-distribution network is limited in most cases, even providing opportunities to free up capacity. Taking the consumer's viewpoint, we highlight the economic importance of the thermal storage tank, which requires a thermal capacity of two to three times the hourly thermal power output of the CHP to optimize electric power production and limit thermal losses. Further increasing the storage tank size can increase the gas-distribution capacity that can be marketed by the distribution system operator, but practical constraints in terms of dedicated land area have to be considered as well.

Figures

Fig. 3. An example of CHP sizing with the largest rectangle under the load-duration curve.

Fig. 6. The peak gas demand increase caused by CHP relative to the original peak demand as a function of the relative storage capacity, averaged per user. The actual peak increase depends on the case, but generally decreases with the relative storage capacity. From an RSC of 7 on, the

Fig. 4. The gas demand for a household with an average heat demand. The grey line is the original, reference gas demand without CHP on a typical cold day. The thick black line is the gas demand for this household with CHP without storage. The gas demand when a 100 L of thermal storage is

Full text

ROBERT SCHUMAN CENTRE FOR ADVANCED STUDIES
Jeroen Vandewalle, Nico Keyaerts and William D'haeseleer
THE ROLE OF THERMAL STORAGE AND NATURAL GAS IN
A SMART ENERGY SYSTEM
EUI Working Papers
RSCAS 2012/48
ROBERT SCHUMAN CENTRE FOR ADVANCED STUDIES
Loyola de Palacio Programme on Energy Policy

EUROPEAN UNIVERSITY INSTITUTE, FLORENCE
ROBERT SCHUMAN CENTRE FOR ADVANCED STUDIES
LOYOLA DE PALACIO PROGRAMME ON ENERGY POLICY
The Role of Thermal Storage and Natural Gas in a Smart Energy System
JEROEN VANDEWALLE, NICO KEYAERTS AND WILLIAM D'HAESELEER
EUI Working Paper RSCAS 2012/48

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ISSN 1028-3625
© 2012 Jeroen Vandewalle, Nico Keyaerts and William D'haeseleer
Printed in Italy, September 2012
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Frequently asked questions

Q1. What are the contributions mentioned in the paper "The role of thermal storage and natural gas in a smart energy system" ?

Vandewalle et al. this paper showed that the technical impact of a massive introduction of cogeneration on the gas-distribution network is limited in most cases, even providing opportunities to free up capacity. 

Q2. What have the authors stated for future works in "The role of thermal storage and natural gas in a smart energy system" ?

Future work will include the analysis of how to determine the local effects in the gas distribution network. 

Q3. how does a peak demand increase increase gas storage?

Increasing the storage size beyond an RSC of 2.3 further decreases the gas demand peak, creating the opportunity to free up capacity in the gas distribution network. 

Q4. What is the impact of CHP on the gas distribution system?

In general, the average gas demand is expected to increase with a rising penetration level of CHP, potentially leading to physically congested pipelines. 

Q5. What is the impact of the CHP on the gas distribution system?

the impact depends on the exact gas demand of the CHPs, and these depend on the use of thermal storage and the interaction between the gas and electricity distribution systems. 

Q6. What is the effect of a massive introduction of CHP?

It can be concluded that, for their cases and assumptions considered, a massive introduction of CHP would not lead to general technical problems, as long as the thermal storage tanks have a capacity of two or more times the hourly thermal output of the CHP. 

Q7. Why is the term adapted annual gas cost used?

The term adapted annual gas cost is used here because the revenues from the produced electricity are subtracted from theannual gas bill. 

Q8. What is the role of gas and thermal storage in smart energy systems?

smart grids focus on electricity, often disregarding the role of gas and thermal storage in overall smart energy systems. 

Q9. What was the funding for this work?

This work was partly funded by the research project on ‘local intelligent networks and energy active regions’ (LINEAR)supported by the Flemish agency for innovation through science and technology (IWT). 

Q10. Why is CHP a dispatchable source of electric power?

contrary to most renewable DER, CHP is a dispatchable source of electric power because of the continuous availability of gas as its fuel. 

Q11. What is the energy balance for the CHP?

Equation (2) describes the heat balance: for every hour t, the heat demand (kWh/h) must be met either by the boiler, the CHP or the storage tank. 

Q12. What is the economic rationale of the customer to use CHP?

Besides studying the technical impact on the gas distribution network, the economic rationale of the customer to use CHP should be investigated as that analysis sheds light on how the gas demand can look like if the role of thermal storage is taken into account. 

Q13. What is the way to keep the CHP running all night?

4. For some heat demand profiles, a RSC of 2.3 is not sufficient to keep the CHP running all night; a higher RSC value would therefore be needed. 

Q14. What is the effect of the buffer size on the peak gas demand?

It can also be noted in Fig. 4. that the line for 100 L shows a fallback of gas demand by night because the buffer is not large enough to store enough heat from the CHP to keep it on all night. 

Q15. How does the peak increase change with the RSC?

The actual peak increase is case dependent— that is why Fig. 6 is not a smooth curve—but in general, it decreases with increasing relative storageJeroen Vandewalle, Nico Keyaerts and William D'haeseleer8capacity, even when an RSC of 2.3 is exceeded, up to an RSC of 7. 

Q16. What is the role of the gas distribution network in a smart energy system?

The natural gas distribution network is represented by a hypothetical model, disregarding the pressure losses and the location of the consumers in the network. 

Q17. What is the effect of increasing the buffer size beyond the optimal value?

Increasing the buffer size beyond the optimal value is also be sub-optimal for the customer due to the extra thermal losses of the tank.