VOL.5, NO.4, DECEMBER 2014
From Beer to Electricity-An Energy Harvesting Experiment in the Forest Nawfal Al-Zubaidi R-Smith1, Anna Maria Polli2 1
Faculty of Electrical Engineering and Communications, Brno University of Technology Email:
[email protected] 2
University of Applied Science Upper Austria Email:
[email protected]
Abstract – within the last years smart phones have become more and more part of our daily lives and the ability to provide enough charging energy for the phones is also becoming a great concern for researchers. The conversion of waste heat to electricity is part of the environmental energy harvesting methods, especially for low-energy consumption systems. This research aims to develop a thermoelectric system that can be used to harvest the consumed heat into electrical energy, which in turn is applied for charging mobile phones at public events.
the use of emergency calls, or just simply contact friends and share their different experiences and adventures in the festival by taking pictures, videos or audio recordings. Even just slightly charging your phone could be helpful for visitors to send a text message in some cases when in need.
1.1 Thermoelectric Generation Principles The thermoelectric phenomenon was first discovered by Seebeck in 1821, and since then the base for thermoelectric energy evolution was established. Seebeck noticed an electrical flow running when a heat gradient was set between two different conductors joint at two parts, so when one conductor was heated and the other was cooled down or maintained at a constant temperature, an electric flow was generated between the two conductors [1][6].
1 Introduction In the last decades, the growth of industry and the increasing demand on energy, which is dragging the fossil-based energy sources to low levels, lead to a profound interest in renewable energy by researchers, governments and companies. Therefore, the work on thermoelectric energy conversion has its importance by researchers [1]. A flexible thermoelectric generator for human body heat energy harvesting providing 2.1 µW was provided by [2]. A thermoelectric generator used for recovering from a vehicle engine was also provided in [3], moreover there has been use of thermoelectric generators to harvest the heat in large industries were a large amount of heat is lost, such as, cement production factories as shown by Bormet et. al. as in Ref. [4]. Recently there has been visious research to improve the figure of merit, but this research is provoked due to the uncontested reference material with specisfied thermoelectric properties. It can be noticed that most of the research in this area is mostly focusing on industries were large amount of heat energy is wasted, so here we apply the thermoelectric consept on low waste heat energy. In this paper we introduce a novel concept of harvesting electricity at festival environments. We introduce an energy harvesting installation, which was deployed in a five day festival entitled Smukfest, in Denmark. At the festival location we have two certainties: (1) people consume a lot of liquids (beer) and need to get rid of it and (2) the festival took place at an open-air space- the forest of Skanderborg, Denmark. For our project we made use of these criteria and tried to gain electricity out of warm waste-fluids. To be more specific, we connected our harvesting installation to the outcome of the urinals and hot showers. Out of its heat we tried to harvest energy. The visitors attending these festivals for some days in a row will surely find the need to charge their electrical devices for
1.2 Related Work Thermoelectric generation has caught the attention of researchers and is developing rapidly; to mention some examples of related work in this area; a flexible thermoelectric generator for human body heat energy harvesting proposed by S.E Jo et.al. [2], in this work the heat difference between the human body and the ambient is harvested, when the heat difference was around 14º Celsius an output power of 2,1 µW was generated. The proposed module was fabricated using dispenser printing thermoelectric materials and the fabricated thermoelectric generator was attached to the human body [2]. This proposed module gave us an inspiration that low heat temperature differences can be taken advantage of to convert it into energy. Accordingly, another application was provided by Ishiyama in [5]. He shows a method to harvest the heat leakage from hot pipes, and the results show that the heat leakage loss was suppressed even when the heat difference was small, on a larger heat-electricity scale Kyono T. et.al in [7] were thermoelectric generation was applied at vapour condencers, taking into account the large amount of heat loss that they produce and converting it into high energy values by a suitable thermoelectric module arrangement, these were some of many applications that consider thermoelectric generation in there principle.
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VOL.5, NO.4, DECEMBER 2014 The different parts used in the module are briefly described next (see in Figure 3).
2 Proposed Module Our project idea was aimed to be applied for the people in the festival to produce their own energy from the waste heat sources available, and charge their electrical devices, mobile phones, iPads, etc. The main concept is to take advantage of the large queues on the hot showers and urinals, where normally that waste is being flushed to the sewer, and convert that waste heat energy to electrical energy in a usable form and use it to charge electrical devices. In this work the module provided was applied on two sources at Skanderborg festival: the Urinals and the showers; regarding the showers there was a last minute change because the waste water was at ambient temperature, so not as hot as expected, though we still applied one harvesting tank at the outcome of the showers, and got minor readings out of it (too minor to go into detail), Figure 1 shows the shower harvesting tank.
Figure 3: Building process of energy harvesting tank
Thermoelectric modules TEC1-12706 from HB Corporation with specifications for each as follows: Number: TEC1-12706; Size: 40 mm * 40 mm; Max operation temperature: 138 º Celsius. These TEG modules have been selected as they are sensitive to low temperature differences. We tested them prior to the installation for low temperatures and they have given promising results.
Dc-Dc step up boost converter, the main task of this converter is to accept an input voltage between 1v and 5v and delivering an output constant voltage of 5v with 500 mA current that is suitable to connect to a USB port.
An Aluminum tank to conserve the waste fluid, the tank was designed with specifications that can provide the best heat conduction to the surface where the Thermo Electric Generator (TEG) circuit is attached; the thickness of the aluminum sheet used to build the tank was thin (0,5 mm) to conduct heat faster to the circuit; it was considered to be aluminum since the thermal conductivity of aluminum is high when compared to other materials, i.e thermal conductivity for Aluminium is 250 (K-(W/m.k)) while for iron its 80 and for steel it is 46 (K-(W/m.k)), which explains our selection of Aluminium for our installation.
The aluminium tank was soldered in a way to conserve a high amount of waste fluid. At the same time, it was important to keep the flow running and hence the hot waste-fluid in the tank will conserve heat, in other words when the fluid was recycling (hot fluid entering the tank and the cold fluid exiting it). Figure 3 shows the installation of the TEG’s on the tank in a series connection.
Figure 1: Shower heat energy harvesting tank The second waste heat source were the Urinals, shown in Figure 2. From this tank we achieved promising results, in comparison to the shower, but as already described, the outcome of the shower was not hot enough.
The insulation for the aluminium tank from the external ambient: polyester insulation sheets were used to reserve the heat in the aluminium tank from being leaked to the ambient. The storage device and chargers: A Lithium-Polymer rechargeable battery were used to store the harvested energy, the battery used had a capacity of 1000 mAh, 5V Dc output and has USB connections for both input and output terminals, so it could be connected to 5V USB phone multiport chargers and charge different mobile phones.
Figure 2: Urinals energy harvesting tank The harvesting modules built for the Urinals and the showers were similar from both the concept and construction, except that there were some differences in the size and pipe connections that had to be taken care of, since the flow coming from the showers was stronger than that of the urinals.
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VOL.5, NO.4, DECEMBER 2014 actual users did when approaching and using our installation, as well as in the sense of conducting the user study outside of the laboratory. In total we conducted 10 semi-structured interviews onsite, with 11 users, since one interview was with a couple. The age ranged from 23 to 27 of the interviewees, which can be clearly attributed to the age group that the concert was aimed at for those 5 days. The installation was deployed two days before the festival started to test out the system in the real setting, apart from the previous tests done in the laboratory. Lastly we recorded from the 5-day festival the full history, when electricity was won and its capacity. This data visualizes the won electricity that illustrates when enough electricity was gained to charge a per-so-nal device. This paper addresses qualitative and quantitative data, in particular the interview data as well as the recordings from a microcomputer that was connected to the output of the aluminium tank that converted voltage out of the urinals. An observational data was ethically not feasible in the urinals and actually there was no need to gain data on that, since the interaction was measured through amount of liquids that the aluminium tank reached. This nouvelle concept was tested prior to seeing if the heat of the liquids in the urinals produces enough electricity to charge one’s phone. Therefore we focused on the interviews to gain insight into users’ experiences and on the quantitative data of the tank, which represents how much electricity was harvested within those 5 days of deployment, and when were the highest or the lowest peeks to harvest electricity. While conducting the interviews, notes were taken from the interviews and those were used for the bottom-up analysis where the text was coded and extracted. In studying what people answered in the semi-structured interviews, few tensions evolved, in respect to being in need for a place to charge a phone versus not being able to distinguish the place from the festival and identify it as a place for charging the phone, or pointing out the multitasking chance as something positive versus the time while using the urinals enough to charge a phone. Accordingly we looked in greater detail at these tensions in the next sections.
2.1 Installation Structure The module was established starting with the soldering of the TEGs on the lower surface of the aluminium tank, adding thermal adhesive paste to transfer heat from the tank to the TEGs efficiently, which is shown in Figure 3. The TEGs were connected in series this choice was taken to provide a higher total voltage and a safer connection for the TEGs, the series connection helps us combine the voltages of the TEGs together whith keeping the same amount of current which helps in getting a higher power output (power = Voltage*Current), afterwards the TEGs were soldered together and isolated with hot glue to protect the connections from the external ambient; such as rain or rough movements. The output of the TEGs connections are connected to the DC-DC step up boost converter, which will boost the output of the TEGs and keep it at a constant flow of 5v and at the same time connect the output to a USB port. Having the USB port as a source from the waste heat harvested energy it makes it easy to connect to the Lithium-Polymer battery and harvest the energy, this helps us harvest the energy produced in the battery and use the battery to charge phones once it has enough energy stored. In this module the battery was used in a dual task simultaneously, to be charged from the waste heat and to be connected to a 10 port USB phone chargers that were considered to be suitable for the installation. On the other surface of the TEGs modules, a cold waste source was connected to a similar aluminium tank with additional heat sinks attached to have the other surface of the TEGs at a lower temperature when compared to the surface attached to the hot waste tank, like this the TEGs are sandwiched between the two tanks, with approximately an average heat difference of 16°C, which changed depending on the tempretaure and amount of fluid in the aluminium tank, a block diagram is shown in Figure 4.
3 Findings and analysis 3.1 Interviews analysis In the interviews we were asking about people’s first impressions of the installation and on the usage in its early stages and compared this qualitative data with the quantitative data to strengthen our findings and analysis. People were mentioning that the application was clear to them right from the start and we observed that the idea of harvesting energy from the urinals was very popular. “I think it is great, and having worked in solar energy I love green energy and you should expand your work further” #1 (see table 1). The data showed that the application of the urinals was higher than the bath application. The bath concept did not really get picked up on in terms of energy harvesting because when put into practice, it turned out to be not an optimal set. The system was designed to convert hot liquids into energy and the output of the showers was simply too cold to win
Figure 4: Installation structure block diagram
2.2 User study and research methodology Over a 5-day period the environmental harvesting installation was deployed at the festival, Denmark’s Smukfest Festival in August 2013. Our approach therefore was a time-limited inthe-wild study [6], both in the sense that we studied what the
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VOL.5, NO.4, DECEMBER 2014 enough amount of electricity to charge one’s phone, since the average electricity harvested from the showers was 0,21 voltage. The heat variance was too small; the difference of the temperatures of the hot and cold aluminium tank was between 3 or 4 degrees, which was not enough. This decision to keep the output of the showers at that temperature was a decision from the management of the festival.
aluminium tanks in that moment. The lower the flow was, The less light was shining, when maximum flow from the urinals reached the tank all lights on the tree shone and visualized that maximum electricity is achieved (see in Figure 5).
Table 1: List of interviews Interview number
Interviewee’s description
Interview #1
Woman, teenager, visiting with her parents
Interview #2
Woman in her mid-60s, visiting alone
Interview #3
Man in his early 40s, visiting alone
Interview #4
A couple (woman and man) in their end-20s
Interview #5
A couple (woman and man) in their 20s
Interview #6
Man in his end 30s, visiting alone
Interview #7
Daughter (early 20s) and father (late 50s)
Interview #8
A couple (woman and man) in their early 30s
Interview #9
Man in his mid-50s, visiting with his family
Figure 5: LED-lights on the trees, visualising the flow intensity in the aluminium tanks gaining electricity to charge per-sonal devices At the time when the urinals sent maximum liquid to the aluminium tank, then the indication of three digital apples (see Figure 8 on the right in a red circle) lit up signalling that maximum electricity had been produced. It was pointed out that the interaction design was not optimal. Interviewees indicated that the light of the tree were difficult to immediately distinguish from all the other lights that were around in the woods from the festival. So for some it was difficult to figure out the connection to the interface and the urinal installation that the higher the lights shone on the tree the more energy was harvested. A further tension was talked about: the Multifunctional opportunity vs. short time to charge. Interviewees talked about a brilliant idea, to “go to the urinal and spend these 3 or 4 min [to] simultaneously charge my phone at the urinal, and you know how precious is having at least some charge in your phone” #3. Or else it was considered to be used in the time when, “my boyfriend is there and I am waiting for him” #4. Few individuals were pointing out hygienic issues in case of usage “to be honest I don’t think I would use it, maybe if it was installed out of the urinal it could be a possibility because you don’t know who was holding those chargers” #4. The biggest concern people emphasized was the time difference between how long it takes to use the urinals and how long it takes to fully charge a phone. This deployed installation, though was not considered to be used to fully charge one’s phone, more in case of an emergency call, to shortly charge the phone, or else for a short-term usage to start with. The last concern that was raised in the early stage of use was that the installation was charging one’s phone and when the person came back to recharge it again, it did not function anymore. “I tried to use it and charge my phone one hour ago it was charging but now it wasn’t I guess it needs time to harvest energy now” #1. In the first place the battery was full to charge one’s phone because there was enough activity and flow coming to the aluminium tanks. In the second place the battery must have been empty due to limited heat that was conducted from the urinals while others were emptying the charged battery. This brings us to show a report about the quantitative history data, (see Figure 6 & 7).
Therefore the interaction design idea in the bath might be considered for the next festival with hot temperature showers, since this version did not highly contribute to the energy harvesting outcomes and results. But to go back to the intensively used application of the urinals, we could witness tensions in, what we predicted about the installation, and about the actual usage of our participants. A Need for a place to charge vs. not being able to see it illustrates the first tension observed in the analysis. Several users were grateful to find a possibility to charge their phones, since they were in a forest with very few opportunities to get access to electricity. “I have been running around to find a place to charge my phone and I was desperate since there were very few places to charge and they were crowded, so to find it here at the urinal was a huge surprise!” #2. This effect was exactly what we design this installation for, but then people on the other hand were mentioning that they believed it was rather a joke “I did notice but as we are in a festival I thought it was a scam or people were making a hidden camera to make jokes because I would have never thought that urinals can produce energy” #5. Others again had difficulties to understand our interaction design idea. With LED-lights mounted on a tree next to the urinals, we visualized the intensity of how much flow was running through the
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VOL.5, NO.4, DECEMBER 2014 Table 2: Sample output readings of Voltage and Current before the boost up converter circuit Reading number
Voltage in V
Current in mA
1
0,208667
1,759
2
0,208667
1,759
3
0,417333
3,51
4
0,417333
3,51
5
0,417333
3,51
6
0,593223
5,0018
Accordingly to the busiest times of the event, the highest peak of usage was from around 18:00 p.m. To 01:00 a.m. in the morning. During the day, there was little flow running through the pipes, so from 02:00 p.m. till the evening little energy was produced (see Figure 6). The power harvested in mWatts is shown in Figure 7, as noticed it is linear with the voltage measurments shown in the previous figure, the times where the tanks where receiving more hot fluid the more power was harvested and during the time when no fluid was entering the harvesting tank the power was almost zero. This data visualizes the gained electricity that illustrates when enough electricity was produced to charge a per-so-nal device, the average consumption of electricity to a charging phone can range from 4,8 to 5,3 Watts, which was the reason why we directly used the harvesting energy to charge a battery slowly and then the battery was used to charge mobile phones.
Figure 6: Graph showing output reading change during different days
3.2 Discussion and future work All in all we can conclude out of our study, that the harvested energy was enough to charge one’s phone, since there was more than one person at the urinals. For this stage of this prototype installation, we wanted to test how much electricity can be produced and if this would be enough to charge a per-sonal device. Even though we had some breakdowns, pointed out by our interviewees, we can fortunately report on an introduction of a nouvelle energy harvesting installation. Since it was the initial prototype that we deployed at the festival, there is enough room for possible future work, starting by exchanging the DC-DC boost converter by a modern power management circuit with maximal power point tracking, which would optimize the harvested energy, further work, could be the development of the interface design. The identified problem of the time for using a urinal and charging a phone varies. If this charging scenario were to be held at another setting, such as a nearby bench or bar, where a more hygienic atmosphere is provided, maybe some degree of social interaction could play a role, where people are staying a little longer than in a urinal. This new place could then have outlets of the energy harvested using the energy of the urinals. All this could be considered for a redesign of the installation deployed at the Denmark’s Smukfest Festival. Depending on our observations and results we can also expand the amount of heat conversion by attaching further thermoelectric generator modules to the aluminium tank surface on a series connection and also increasing the
Figure 7: Graph showing power results at different hours From the first test of the installation the results were exciting, the urinals started to produce energy through the tank. On the first day of the festival it started to become crowded at about 18:00 pm. The main stage of the musicians was near our installation and people started to use them. The first reading of Volt we got out from the installation, started by 0,208667. The ambient temperature was low and the tank itself was on low temperature so it took about 25 min of use till the reading jumped to 0,417333 V and was maintained at that reading for some time. It went higher to 0,59322 V during higher usage of the urinals (see Table 2), at that time the circuit and boost up converter starting charging the battery at a 5 Volt output and people were able to charge their phones from the outlet chargers. Additionally, on the system, a microcomputer was installed with a radio transmitter to transmit the readings on time intervals to our servers at the base, and we were able to keep up to date with the results obtained from the harvesting tank. The average time people used the installation was five to ten minutes, and after that retuned back to the festival.
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VOL.5, NO.4, DECEMBER 2014 effect of the heat sink to maintain the cold side at a lower temperature, which could also be done by waste from the festival site such as ice remains from different bars in the area, or a cold water source from the bars around.
[3] ZHANG, Zheng, Xiaopeng XIE, Yutao LUO, Jiang Hong WU a Guang Shu SI. Research on the novel high-intensity thermoelectric generator and its application on HEV. ICT 2005. 24th International Conference on Thermoelectrics, 2005. 2005, roč. 48, č. 16, s. 892-895. DOI: 10.4028/0-87849410-3.892.
4 Conclusions [4] BORRNERT, Thomas, Thomas BURKI a Michigan State UNIVERSITY. Waste heat conversion into electricity. 2010 IEEE-IAS/PCA 52nd Cement Industry Technical Conference. 2010, č. 1. DOI: 10.2172/1045212.
This paper has discussed the installation done in Smukfest Festival to convert hot waste-fluids (Shower and Urinal) into a usable form of energy to charge a battery and use it for charging phones for the festival visitors, results showing voltage, current and power eadings are shown. The concept is based on converting heat to electricity, which was implemented in a circuit to make the energy in a usable form and harvest it or use it directly to charge mobile phones. Several parameters were taken into consideration, such as the availability of waste sources in festivals, the visitors’ energy source needs at open air events, the isolation requirements and the continuance of the installation. The installation should have positive results as the readings from the tank were above 0,5 volt at some time intervals as shown in the output graph, with an approximate current of 0,5 mA, and was connected to a boost-up amplifying circuit to provide 3-5 volts and charge the battery. We were able at some times to charge a phone from the battery and at some times more than one, depending on the status of the battery. This paper shows step by step the procedure used to build the installation, the equipment used and the readings and results, as well as the user’s studies performed on the visitors of the festival.
[5] EAKBURANAWAT, Jensak a Itsda BOONYAROONATE. Development of a thermoelectric battery-charger with microcontroller-based maximum power point tracking technique. Applied Energy. 2006, vol. 83, issue 7, s. 687-704. DOI: 10.1016/j.apenergy.2005.06.004. [6] BROWN, Barry, Stuart REEVES, Scott SHERWOOD, David G. BEER, F.M. KIHANDA, G.P. WARREN a A.N. MICHENI. Into the wild: Clinical Challenges and Opportunities. Proceedings of the 2011 annual conference on Human factors in computing systems - CHI '11. 2011, č. 1, s. 471-486. DOI: 10.1007/978-1-4020-5760-1_44. [7] KYONO, T., R.O. SUZUKI a K. ONO. Conversion
of unused heat energy to electricity by means of thermoelectric generation in condenser. IEEE Transactions on Energy Conversion. 2003, vol. 18, issue 2, s. 330-334. DOI: 10.1109/tec.2003.811721.
Acknowledgements We thank all the guests, staff, and volunteers from the festival, and all publications support and staff, who wrote and provided helpful comments on previous versions of this document. Some of the references cited in this paper are included for illustrative purposes only. The work has been sponsored by the InfinIT network with funding from the Danish Agency for Science, Technology and Innovation.
References [1] PUNNACHAIYA, S., P. KOVITCHAROENKUL a D. THONG-ARAM. Development of low grade waste heat thermoelectric power generator. Songklanakarin Journal of Science and Technology. 2010, roč. 32, č. 3, s. 307-313. Dostupné z: Available in Scopus. [2] KIM, M.K., M.S. KIM, S.E. JO a Y.J. KIM. Flexible thermoelectric generator for human body heat energy harvesting. Electronics Letters. 2012, vol. 48, issue 16, s. 1015-1017. DOI: 10.1049/el.2012.1566.
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