Pre-MSc Research Paper - Renewable Energy Logistics
Self-sufficient households with wind and hydrogen energy
University of Groningen, Faculty of Economics and Business
Lecturer: Jan Eise Fokkema
2
Abstract
Purpose: The purpose of this paper is to investigate the possibility to meet the heat demand of
self-sufficient households with the use of a hybrid heat pump, running on sustainable wind energy or converted hydrogen energy. Most of the households in Europe nowadays still heat their houses with fossil fuels, which are harmful to nature. This research is conducted to find an answer to the question: ‘How affects the windmill park size the hydrogen storage necessities
to meet the heat demands of the self-sufficient households using a hybrid heat pump?’
Methodology: A simulation study is performed to find an answer to the research question. The
simulation model involves wind energy production, heat demand, and a beginning hydrogen inventory. Three different analysis has been performed. These analyses provide insights on the possibility to be self-sufficient. First, the base case is analysed. Secondly, the WPPC is analysed. Finally, the beginning hydrogen inventory is examined. The data used for this research are hourly produced wind energy and hourly heat demand.
Findings: The results of the performed analysis showed that it is possible to be 100%
self-sufficient, with the heat provided by a hybrid heat pump running on wind energy or stored hydrogen. Because of fluctuating wind energy production, storage was needed to bridge the times there was not enough energy produced to meet the heat demand. The results showed that a changing WPPC and a changing beginning hydrogen inventory influenced the self-sufficiency. Without a beginning hydrogen inventory, there were times in the beginning of the year where there was no energy available to meet the heat demand.
Conclusion: Findings indicate that it is possible for the households to be self-sufficient for
3 Content
Abstract ... 2
1. Introduction ... 4
2. Theoretical background ... 5
2.1. Hybrid heat pumps ... 5
2.2. Wind energy storage as hydrogen... 6
2.3. Self-sufficient households ... 7
3. Methodology ... 7
3.1. Problem description ... 8
3.2. Conceptual model ... 9
3.3. Component list ... 9
3.4. Logic flow diagram... 10
3.5. Assumptions and simplifications ... 11
3.6. Experimental setup... 11
4. Findings... 13
4.1. First analysis: Base case ... 13
4.2. Second analysis: Wind park peak capacity ... 15
4.3. Third analysis: Beginning hydrogen inventory ... 16
5. Conclusion & discussion ... 18
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1. Introduction
195 countries all over the world have signed the Paris Agreement in 2015. In this agreement, all countries came to an agreement to take action for a sustainable low carbon future. A low carbon future can be achieved by using renewable energy instead of non-renewable energy (Paris Agreement, 2015). Renewable energy is energy that is generated from natural resources such as the sun or the wind. One problem is that in 2017, 82.5% of households in Europe are still running on non-renewable energy (Eurostat 2020). To use fewer fossil fuels, renewable energy is needed to run the households on. In contrast to non-renewable energy, renewable energy is accompanied by a crucial problem: fluctuation depending on weather conditions, complicating matching of energy supply and demand. (Sims et al., 2011).
One renewable energy source that can be used to heat households is wind energy from a windmill park. Wind energy is expected to be the most installed capacity renewable energy source in the world in the future (IEA, 2003). But, specific weather conditions can lead to a surplus of renewable wind energy at peak times according to Fanone, Gamba & Prokopczuk (2013).
One solution for heating a household with renewable energy is using a hybrid heat pump. A hybrid heat pump is an electric heat pump, which can heat households with renewable energy. The use of a hybrid heat pump is one of the fastest and cheapest ways to reduce gas consumption in existing houses (den Ouden, B. & Graafland, P. & Bianchi, R. & Friedel, P. 2017). Szekeres & Jeswiet (2018) conducted a research about heating households with heat pumps, with electricity from fossil fuel. This study is different because the electricity comes from the renewable energy source, the wind and uses a hybrid heat pump. Also, this study is about creating self-sufficient households, which do not need non-renewable energy. Self-sufficient households are in this study households that run only on the renewable energy source wind.
In this study, the generated energy from the wind park will go straight to the households, the surplus of energy will be converted into hydrogen using an electrolyser. Then, the hydrogen will be stored, so that this energy can be used when there is a shortage in the produced wind energy. The hybrid heat pump runs partly on electricity and partly on hydrogen. Until now, there is no research about households with a hybrid heat pump, provided with energy from windmill parks.
self-5 sufficient. This study will research a group of households that heat the house completely on energy generated from the wind or converted wind energy into hydrogen energy, with a hybrid heat pump for every house. A hybrid heat pump will be used, because a hybrid heat pump is running on electricity, in this case, green electricity, and so the households use only sustainable energy.
The research question is:
‘How affects the windmill park size the hydrogen storage necessities to meet the heat demands of self-sufficient households using a hybrid heat pump?’
The structure of this paper is as follows: the second chapter is about the theoretical background and the conceptual model. In the third chapter, the methodology is described. The fourth chapter presents the findings of this research. The fifth chapter presents the conclusion, the discussion and will give an answer to the research question.
2. Theoretical background
In this chapter, the literature review of this research about heating a group of self-sufficient households with a hybrid heat pump, which runs on wind energy, is presented. This research is different from existing studies because this study is about self-sufficient houses running on a hybrid heat pump, which is provided with energy from the renewable energy source wind or hydrogen energy, which is converted from wind energy into hydrogen energy. The literature has not yet described the relationship between the possibilities to meet the heat demand of self-sufficient households, provided by green wind energy, and converted electricity from the hydrogen storage. Hopefully, this research will contribute to the existing studies of renewable energies.
2.1. Hybrid heat pumps
6 The conclusion of their research was that 109.3% of the total requirements for the houses could be provided. In the summer, the efficiency of the hybrid heat pump was higher than during the winter period. But, this can conclude that it is possible to provide houses with only green energy.
The conducted researches above are all different than this study because it is not yet done to do a research about a wind/hydrogen system and hybrid heat pumps, working on this energy. The study of Appleyard (2016), shows that there already has been done a study about heating 1500 households with a heat pump, but in his study, solar energy is used instead of wind energy. The conclusion of the study of Appleyard (2016) is promising because the study was successful. This means that this conducted study also can become a successful one. The study of Zhang et al., (2016), show that it is possible to provide houses with energy for a whole year using a hybrid heat pump. But that study was conducted with solar energy instead of wind energy. Also, the study of Zhang et al., (2016) used a GWSHP instead of a hybrid heat pump. Both of the studies above did not store the surplus of energy as hybrid energy and do not use this stored hybrid energy when there is a shortage in the provided energy.
2.2. Wind energy storage as hydrogen
7 In the researches above, wind energy is researched. According to Caralisa et al., (2019), curtailment has occurred since the 90ies. Curtailment is a waste of energy that could be used, so in this study, the surplus of wind energy is going to be stored as hydrogen and used when there is a shortage of energy. The conversion loss will be 0.7 when the wind energy is converted from energy to hydrogen. The difference from this study compared to others is that only the surplus of wind energy is going to be stored as hydrogen. This stored energy will be used when there is a shortage of energy. According to Liu et al., (2019) storage is expensive, but in this study, costs are not taken into account, there is attempted to find out if the households are able to be self-sufficient with the help of storage.
2.3. Self-sufficient households
Net-zero energy or carbon-neutral housing has become a driving force toward achieving green building design strategies (Chang, Rivera, & Wanielista. 2011). The utilization of renewable energy for zero-energy buildings mainly includes solar photovoltaic technology, solar thermal technology or ground source heat pumps (Tan, H. 2016). Various studies have researched solar heating systems for buildings (Ortiz. M, & Barsun, H. & He, H. et al. 2010). The study of (Ortiz et al., 2010) concluded that only in the months of December and January there was not enough energy available from the sun to heat a building in the United States. (Islam, S. & Dincer, I. & Yilbas, B. 2019) did a study to meet the electricity and heating demand for a farmhouse in Saudi Arabia with solar energy.
There are a lot of studies about self-sufficient households/buildings. But, most of these studies are about self-sufficient households, which use solar energy. Also, no literature is about heating self-sufficient households with wind energy and when there is a shortage, with energy coming from the converted hydrogen storage. This study is different from the studies above because the electricity will come from wind energy and the households will be heated with a hybrid heat pump. It is important to conduct this study because when the households are heated with a hybrid heat pump, the houses are heated with only sustainable energy. Also, this study will research heating a group of households instead of one house or building as above mentioned.
3. Methodology
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3.1. Problem description
The main problem addressed in this paper is concerned with what the size of the wind park peak capacity needs to be, in order to be self-sufficient with renewable energy, using a hybrid heat pump to heat the house. The problem is that it is not yet known if the households could be self-sufficient with renewable energy. This will be tested for a whole year. Because it is tested for a year, the study shows the different results for the summer and winter periods. In winter there is more demand for heat, but there is also more wind energy generated. A wind electricity producer is considered and uses the total capacity of a windmill park w (MW) and a hydrogen storage tank s. The amount of energy needed will go straight to the houses, the surplus is stored. The amount that will be stored in the hydrogen storage tank during every hour t, depends on how much from the production of energy is needed for all the houses every hour. In this way, it can be seen if a group of households are able to be self-sufficient, during the whole year.
3.1.1. Parameters and variables
The parameters in this research are the inputs of the model and the variables are the outputs of the model. The inputs of this research are the wind park peak capacity (WPPC) in MW, the hourly heat demand in MWh, self-sufficiently, and the beginning hydrogen inventory in MWh. A household is self-sufficient if it runs on renewable energy.
Based on the inputs, the model will generate different outputs. The outputs are the amount of the produced wind energy in MWh, the destination of the produced energy in percentages (straight to households or into storage), and the times there is no energy to supply the heat demand. All these outputs are based on hourly decisions. In the figure below (figure 1), the simulation model is shown. The model shows the inputs, the simulation of the model, and the outputs.
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3.2. Conceptual model
The objective of this study is to gather insight into how a group of households can be self-sufficient households, using a hybrid heat pump and wind energy. The study starts with the input form a windmill park. Here comes the energy from. The amount of energy produced by these windmills determines if the group of households have enough energy to heat the house for a year. Also, the demand of the households for a year is known in advance. Besides this, hydrogen storage has unlimited capacity. The objective will be reached by using a simulation model. A simulation model offers the possibility to model non-existing infrastructures (Robinson, 2004).
Figure 2 Conceptual model
The conceptual model in figure 2 shows in a very short way how the mechanism of this research is. The generated energy goes to the households if needed and if the households have enough energy, the surplus goes to the hydrogen storage tank, to be converted into hydrogen. Once there is a shortage of wind energy, then this need for heat can be provided from the hydrogen storage tank.
3.3. Component list
The component list shows which components are included/excluded in this research.
Table 1 Component list
Component Detail Include/exclude Comment
Wind energy Production Included The production of wind energy
Demand Household Included Hourly heat demand from
1500 households
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Costs Excluded Out of scope
3.4. Logic flow diagram
The figure below gives an overview of the logic flow of the simulation model of this paper. The figure begins by generating wind energy. The produced energy goes to heat demand. When there is more energy produced than needed, the surplus will be converted into hydrogen and stored. When there is not enough energy produced, the heat can be taken from the hydrogen storage. When there is not enough energy from production and there is no energy in storage, the heat needs to be from a different energy source. This will mean that the household is not self-sufficient. The time horizon for this paper is one year. Starting on 1 January 2008 and ending on 31 December 2008. The diagram starts with energy production. This produced energy goes to heat demand. If there is not enough energy produced, the energy needed for the demand comes from the stored hydrogen energy. If there is not enough energy in storage, the heat demand is not met. If there is more energy produced than needed, the surplus of energy goes to the hydrogen storage. This process repeats every hour for one year.
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3.5. Assumptions and simplifications Assumptions
The following assumptions are made for the simulation:
- The hydrogen storage capacity is unlimited. This is not the main target of this research. - The conversion loss from wind energy to hydrogen is 30%. (Ananthachar, V. & Duffy,
J. J. 2005). There is no conversion loss from hydrogen to energy.
- The households are well isolated. This is included so the used energy will completely be utilized.
- The hourly provided data is reliable.
Simplifications
The following simplifications are made for the simulation:
- The model will use data of one year, the year 2008. The average yearly heat demand is used from 1500 households together.
- Costs are not taken into consideration.
3.6. Experimental setup
The data used for this experiment are the total energy production of a windmill park in MW and the heat demand from 1500 households in 2008. The data for the hourly heat demand is provided by Liander and is from the year 2008 (Liander, 2008). This data is transformed from the average gas consumption times the amount of households. The outcome of the average gas consumption times the amount of households, times the hour fraction, is the heat demand in MWh every hour during the whole year. The total heat demand over the whole year is 509 MWh. The data for hourly wind energy production comes from KNMI. The data for hourly wind production is provided in MWh. The production of wind energy is dependent on the WPPC. The conversion of hydrogen production using an electrolyzer is around 70%, in this case, because with converting energy, some energy is lost (Ananthachar, V. & Duffy, J. 2005).
12 Table 2 presents the experimental setup starting with the base case. Secondly, the WPPC experimental setup is presented. At last, the beginning hydrogen inventory is shown. These three different experiments are further explained in the following paragraphs. In total, 22 experiments are conducted.
Table 2 Experimental setup
Set of Number Size windmill Demand Storage Experiments of experiments park (MWh) Households capacity (MW)
(MWh)
Base case 1 1 512 Unlimited
Wind park 5 0.5 till 2.5 512 Unlimited
peak capacity
Beginning hydrogen 16 0 until 15 512 Unlimited inventory
3.6.1. Base case
The base case of this study is based on the average power of a windmill and the average hourly heat demand of 1500 households. The average power of a windmill is 1 megawatt (MW) and the average yearly gas demand of one household is 2990 kWh (Nibud 2019). In the base case, the total demand of households is 509 MWh, the WPPC is 1 MW and the beginning hydrogen inventory is 1 MWh. The total heat demand comes from 1500 households and their average demand during the whole year. The WPPC is set at 1 MW because this is the average capacity of a windmill (Rijn sd). The beginning hydrogen inventory is set at 1 MWh because then there is small storage in advance to provide energy when there is nothing produced yet. The goal of this research is to find out how the size of the wind park influences the supply of heat to a group of households. Per month, the percentage of the destination of the produced heat is calculated.
Table 3 Base case
Base case MWh
Heat demand 509
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Beginning hydrogen inventory 1
3.6.2. Wind park peak capacity
The second analysis is about the WPPC. This analysis will be performed to see what changing the WPPC does to the production of energy. With these different amounts of energy production, it can be find out if there is enough energy to supply the demand and if the households are able to be self-sufficient with these amounts of produced energy. This analysis will research the different WPPC, from 0.5 MW up to and including 2.5 MW. These values of WPPC are chosen because with a peak park capacity of 0 there is no production at all and with a larger amount, there is way too much energy produced. This analysis will be performed, to find out if a group of households are able to be self-sufficient with wind energy with these amounts of energy produced. With this analysis, also the destination of the produced energy is calculated in percentages. The destination means if the produced energy goes to the households or to the hydrogen storage. Every time the WPPC increases, the produced wind energy increases.
3.6.3. Beginning hydrogen inventory
In this analysis, the beginning hydrogen inventory is researched. The research starts without any storage built up yet because in this case the storage tank is newly built before the beginning of the year. A year starts on the first of January. In January, there is much demand for heat in households. When there is no hydrogen storage yet, there will be times that there is no energy to supply the households. Therefore, this analysis researches what the changing beginning hydrogen inventory does to the self-sufficiency of the households. The beginning hydrogen inventory varies from 0 MWh until there is every hour of the year enough storage to supply the households with heat. The heat demand stays the same and the WPPC is set at 1 MW. These values have been chosen, because there is searched for an inventory where there is always enough energy available (produced or in storage) to meet the demand.
4. Findings
In this chapter, the main results of the research are presented. In total, there are three analyses performed. Every performed analysis will be explained separately.
4.1. First analysis: Base case
14 divided into the percentage which is needed for heat demand and the percentage which is a surplus and goes to the hydrogen storage.
Table 4 Base Case
Month Wind energy produced % to demand % to hydrogen storage (MWh) January 95.91 44.36% 56.21% February 85.55 44.41% 55.59% March 113.18 38.29% 61.71% April 63.18 31.94% 68.06% May 107.36 19.82% 80.18% June 87.27 10.15% 89.85% July 80.64 5.81% 94.19% August 59.36 6.10% 93.90% September 88.18 9.03% 90.97% October 86.46 20.54% 79.46% November 165.36 22.95% 77.05% December 99.45 43.19% 56.81%
Table 4 shows that in the base case, a larger share of the produced energy goes to storage than to heat demand. This means that every month of the year, there is more energy produced than there is heat demand from the households. The WPPC in the base case is 1 MW. The table shows that in November, March, and May, the most energy is produced. In January, the biggest percentage from the produced energy is intended for the heat demand. In August, the lowest amount of energy is produced. In the figure below, the destination of the produced energy is shown graphically.
15 In figure 4, it can be seen that the percentage of storage every month is higher than the percentage for the demand. This means that every month, there is more energy produced than the demand of the households. Every month there is a surplus of energy, which is converted into hydrogen. In the months, January, February, and December, the percentages which go to the heat demand are the highest. In these months, the heat demand is also the highest. In the summer months of June, July, and August, there is hardly any energy needed to heat the households. Especially in July and August, there is a small amount of heat demand.
The percentage which goes to demand is not always equal to demand. With the current settings of the model, also heat demand is provided with energy from the storage. Table 5 shows that most heat comes from energy production, but a part also comes from storage.
Table 5 Heat demand
Month Heat demand % from production % from storage
January 80.59 MWh 52.79% 33.06% February 73.33 MWh 51.81% 48.19% March 67.95 MWh 63.78% 36.22% April 45.45 MWh 44.39% 55.61% May 32.19 MWh 66.11% 33.89% June 14.76 MWh 60.01% 39.99% July 8.31 MWh 56.43% 43.57% August 8.21 MWh 44.16% 55.84% September 15.46 MWh 51.52% 48.47% October 37.54 MWh 47.30% 52.70% November 53.34 MWh 71.15% 28.85% December 72.19 MWh 59.51% 40.49%
The level of self-sufficiency in the base case is 100%. Every month, there is more energy produced than heat demanded. This means, that during the whole year, the households are self-sufficient. The heat for all households comes from wind energy or hydrogen storage and there is no non-renewable energy source needed. In the base case, the households are self-sufficient and this means that it is worthwhile to build these households.
4.2. Second analysis: Wind park peak capacity
16 these different amounts of WPPC in MWh, the produced wind energy is calculated. Every time the WPPC increases, the produced wind energy increases. With a capacity of 2.5 MW, there is in total of 2830 MWh energy produced. This is 5.5 times more than the total heat demand of 1500 households. Only 18% of the total produced wind energy is needed for the heat demand, with a WPPC of 2.5 MW.
Table 6 Wind park peak capacity
Wind park Energy produced Heat demand % Produced energy peak capacity (MWh) (MWh) used for heat demand
0.5 566 MWh 509 MWh 89.93%
1 1132 MWh 509 MWh 44.99%
1.5 1698 MWh 509 MWh 30%
2 2264 MWh 509 MWh 22.50%
2.5 2830 MWh 509 MWh 18%
Table 6 shows that with an increasing WPPC, the produced energy increases and is more MW than the demand is. With a WPPC of 0.5, there is more energy produced than there is heat demand from all the households. With a WPPC of 1 MW, there is already two times more energy produced than needed for the heat demand of the households. Anytime the WPPC increases by 0.5 MW, the amount of energy produced increases. The bigger the WPPC, the smaller the percentage of the produced energy which is needed for heat demand. This means that households during the whole year are able to be self-sufficient. There is enough energy produced. However, this is the total amount of produced energy during the year. There cannot be seen that for every hour there is enough energy.
4.3. Third analysis: Beginning hydrogen inventory
17 Figure 5 Hydrogen storage
Figure 5 shows that the storage inventory is increasing during the whole year. The figure is starting without any hydrogen storage and it looks that the whole year there is enough energy to supply the heat demand. After a year, there is hydrogen storage of almost 400 MWh. Zooming in on the first month of the year (January), the figure looks like figure 6 below.
Figure 6 Hydrogen storage January
18 was not enough energy to provide heat. This happened because the demand was higher than the amount of energy produced. In these first 237 hours of the year, there was not enough storage built up yet. Therefore, there were moments in the year that the households were without the energy to heat the households. In these hours, the households were not self-sufficient.
In the table below, the amount of times there is no hydrogen energy available during the whole year is presented.
Table 7 Beginning hydrogen inventory
Beginning hydrogen No hydrogen Beginning hydrogen No hydrogen inventory (MW) in storage inventory (MWh) in storage
0 MW 128 hours 8 MWh 43 hours 1 MW 116 hours 9 MWh 32 hours 2 MW 109 hours 10 MWh 24 hours 3 MW 96 hours 11 MWh 12 hours 4 MW 87 hours 12 MWh 5 hours 5 MW 77 hours 13 MWh 0 hours 6 MW 67 hours 14 MWh 0 hours 7 MW 55 hours 15 MWh 0 hours
With a beginning hydrogen inventory of 0 MWh, there are 128 hours when there is no energy available for the heat demand. 128 hours of a year is 1.46%, which is a small percentage of the total times there is energy available. With a beginning hydrogen inventory of 12 MWh, there are only 5 hours when there is no hydrogen energy available for the heat demand. With a beginning hydrogen inventory of 13 MWh, there is always enough hydrogen energy available for the heat demand. This means that with a WPPC of 1 MW, a heat demand of 509 MWh, and a beginning hydrogen inventory of 13 MWh, there is the whole year energy available for the heat demand. With these values, the households are 100% self-sufficient. So, with a beginning hydrogen inventory of 13 MWh, households are able to be self-sufficient the whole year and do not need a now-renewable energy source. This means that it is possible for households to be self-sufficient, using a hybrid heat pump that runs on wind energy.
5.
Conclusion & discussion
non-19 renewable energy. Providing households with heat using a hybrid heat pump, makes the households sustainable. Wind energy production is used to provide the households with energy and the surplus of this energy is converted into hydrogen to be stored and to use in times when there is a shortage of energy. This is understood to be the first study that analysis this relationship.
To answer the research question: ‘How affects the windmill park size the hydrogen storage
necessities to meet the heat demands of the self-sufficient households using a hybrid heat pump?’ the research has been executed. The answer to this question is as follows. The WPPC
influences the amount of produced energy. Without any beginning storage inventory, there is not enough wind energy produced to meet the demand of households, because, in the first month of the year, there are moments when demand is higher than the production. It is possible to create self-sufficient households using hybrid heat pumps for heating the households. These self-sufficient households are able to be 100% sustainable.
The outcome of this research can be used when building self-sufficient households in the future. These households can become completely self-sufficient with the use of hybrid heat pumps. With the use of a hybrid storage, the households always have renewable energy available. So, these households are a possible solution for a low carbon future.
There are some limitations to this study. Firstly, this research is conducted for one whole year. If the research will be performed another year, the data will be different. This influences the repeatability of the research. Also, the research is conducted with heat demand from 1500 households. A different sample size can lead to different outcomes. The bigger the sample size, the better the external validity. Also, the data for heat demand comes from the year 2008. To make the research more reliable, using more recent data is better.
Secondly, there are times that there is not enough energy to supply the heat demand. When this happens, there is going to be needed other energy from another energy source. The focus of this research was on the heat demand of self-sufficient households.
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