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At the 39th Photovoltaic Specialist Conference in Tampa, Florida, there were two important and interesting topics which were of particular interest to me.

The first one was covered by Harry A. Atwater, California Institute of Technology (http://daedalus.caltech.edu/research/thinfilmpv.php) “Full Spectrum High Efficiency Photovoltaics” [1]. He was discussing a new concept: splitting the incident solar spectrum into its constituent wavelengths, guiding these different wavelengths into solar cells with different bandgaps, then absorbing them (shown in Figure 1). In theory, the efficiency of such thin film solar cell system can range from around 30% to over 50%. One way of splitting incident light is to use specially engineered nanostructures printed on the surface of a solar cell or planar holographic elements. In the latter case, the solar spectrum is split four ways via a stack of three sinusoidal volume Bragg gratings, where three bands are diffracted at different angles and the 4th band passes through un-diffracted. Four such stacks guide each band to the appropriate solar cell. Each solar cell is composed of two lattice-matched and current matched III-V subcells grown on either GaAs or InP substrates. In addition, because the diffraction grating is sensitive to the incident angle of incoming light, to achieve high concentration with spectrum splitting, a two-stage compound parabolic concentrator (CPC) is used after the holographic elements. The parameters for the primary and second CPC are carefully optimized.

Figure 1 of Xianqin's blog

Figure 1. A scheme illustrating the geometry of eight- junction holographic spectrum-splitting cell with indicated band-gaps and materials

The second topic that was of great interest to me was the progress made in developing flexible thin film solar cells. Since there are an increasing numbers of applications for photovoltaic devices that demand flexible, lightweight solar cells, the research on thin film solar cells on flexible substrates is attracting a lot of attention. The greatest challenge is to lower the cost of production of such devices while maintaining good efficiency in light conversion. There were quite a few talks and posters about this interesting topic during the conference in which the ideas of using tape, metal or polymer as a flexible substrate were discussed [2,3].   I found Kelly Trautz’ talk [2] on epitaxial lift-off (ELO) technology used in MicroLink’s solar cells particularly interesting because it allows flexible solar panels to be made. It also allows one to reuse the substrates on which the cells are grown multiple times.

Xianqin's picture

-Xianqin Meng

Postdoctoral Fellow

Department of Engineering Physics

McMaster University

References

[1] H.A. Atwater et all. “Full Spectrum Ultrahigh Efficiency Photovoltaics”, in 2013 39th IEEE Photovoltaic Specialists Conference (PVSC), 2013.

[2] Kelly Trautz et all, “High Efficiency Flexible Solar Panels”, in 2013 39th IEEE Photovoltaic Specialists Conference (PVSC), 2013.

[3] B. M. Kayes, L. Zhang, R. Twist, I.-K. Ding, and G. S. Higashi, “ Flexible Thin-Film Tandem Solar Cells with >30% Efficiency”, in 2013 39th IEEE Photovoltaic Specialists Conference (PVSC), 2013.

I had the opportunity to go to PVSC 39 in Tampa, Florida with fellow Highly Qualified Personnel (HQP). There were a lot of interesting speeches but I will only focus on a couple of them here – particularly those focusing on CdTe thin films progress. CdTe is one of the most attractive materials for production of low cost thin film solar modules [1]. The record efficiency for CdTe solar cells has been established to be 16.7% for 10 years. In the past 2 years, the CdTe record was broken several times and increased from 16.7% to 18.7%. However, there has been no significant change in the open-circuit voltage which was in the range of 840-860 mV for over 20 years. Many arguments have been made to justify the apparent Voc limitation, most frequently: poor hetero-interface with CdS, the difficulty in doping polycrystalline CdTe, midgap defect levels, or non-uniformities at the nano- or micro-scale. Paths for open-circuit voltage above 900 mV are:

  • Doping: Increasing doping level of CdTe is believed to increase the built-in potential and reduce recombination at the back-surface. Present doping levels are of the order 1014 /cm3 and different ways are proposed to increase them.
  • Lifetime: Higher lifetime(s) are expected to be a sign of less recombination in the junction and quasi-neutral region, and, hence, improved Voc and carrier collection. With higher lifetime, it is expected that a greater fraction of the recombination may occur at the back-contact due to increased electron diffusion through the absorber.

Gloeckler from First Solar announced a new record efficiency of 19.1% for CdTe, although not yet certified by NREL.

Despite these promising results, the gap between solar cell and module efficiencies is still wide (3-5%) [2]. This so-called “solar gap” constitutes a major challenge for commercial viability of photovoltaics. One explanation, proposed by M. Alam and his group at the University of Purdue, says that the “solar gap” is due to the monolithic series connection of thin films that causes shunt leakage current. Analysis of the shunt leakage current show that an I-V curve can be modeled by the diode equation and the shunt current, which has a non-linear relation with the voltage, as shown in Fig. 1. It was shown by Alam et al, that as a consequence of the series connection of cells, large shunts have a twofold impact on module performance. First, they modify the operating point of their neighboring good sub-cells, thereby lowering their output power. Second, a large fraction of this (already reduced) power, generated by the neighbours, is consumed by the shunted sub-cell. Interestingly this phenomenon is not unique to CdTe photovoltaics but more of a universal phenomenon and studies on CdTe, CIGS, OPV and amorphous silicon thin films show the same behaviour. At PVSC they have described a post-deposition scribing technique for electrically isolating these distributed shunts in monolithic thin film PV modules. The localized scribes minimize the losses due to defective shunts by restricting lateral current drain from its (otherwise defect-free) neighbors.

Figure 1 of Ahmed's blog

Fig. 1 Measured IDark (squares) can be represented by a parallel combination of diode with series resistance I (green), and a parasitic shunt component (red), with a symmetric (around V = 0) non-Ohmic voltage dependence. Reproduced from [3] with permission of The Royal Society of Chemistry.

References:

[1] W. N. Shafarman, “What’s next for Cu(InGa)Se2 Thin Film PV: Opportunities and Challenges”, 39th IEEE Photovoltaic Specialists Conference, 2013

[2] S. Dongaonkar, M. A. Alam, “Reducing the Cell to Module Efficiency Gap in Thin Film PV using In-line Post-Process Scribing Isolation”, 39th IEEE Photovoltaic Specialists Conference, 2013

[3] S. Dongaonkar, S. Loser, E. J. Sheets, K. Zaunbrecher, R. Agrawal, T. J. Marks, and M. A. Alam, “Universal statistics of parasitic shunt formation in solar cells, and its implications for cell to module efficiency gap,” Energy & Environmental Science, vol. 6, pp. 782–787, 2013

Ahmed Gabr's picture

-Ahmed Gabr

Ph.D Candidate, Year 3

SUNLAB, University of Ottawa

I recently had an opportunity to attend the 39th IEEE Photovoltaics Specialists Conference in Tampa, Florida (http://www.ieee-pvsc.org/PVSC39/). Since I am just starting to work in Photovoltaics, it was a great opportunity for me to get immersed in this very quickly developing field by listening to high quality presentations given by the leaders of the field. The presentations were divided into 11 topic areas, with a few sessions taking place at the same time. I really wanted to be in a few rooms simultaneously, but with my background in quantum theory I decided to focus mostly on attending sessions from research Area 1: Fundamentals and New Concepts of Future Technologies.

I found a talk by Megumi Yoshida from Imperial College London :“Progress towards Realizing Intermediate Band Solar Cell – Sequential Absorption of Photons in a Quantum Well Intermediate Band Solar Cell” particularly interesting. I was familiar with the concept of introducing the intermediate band (IB) into the solar cell to improve the absorption of photons with energy lower than the band gap energy (see Fig 1 (a)), however this talk took this concept one step further. The intermediate band solar cell (IBSC) can be created introducing quantum mechanically confined structures such as quantum wells and quantum dots [1] into the solar cell. In such cases, the IB arises from the confined states of the electrons in the conduction band (CB) potential.  In theory, by introducing the IB the current can be enhanced by two step absorption of long wavelength photons without reducing the voltage, hence leading to higher conversion efficiency (thermodynamical limit of 46.8% at 1 sun [2]), than a single bandgap solar cell (31.0% at 1 sun).

Figure 1 of Anna's blog

Fig. 1. Energy diagram of an (a) IBSC and (b) IBSC with photon rachet band (RB), in which extra photocurrent is produced due to sequential absorption of sub-bandgap photons increasing theoretical limit in the conversion efficiency. Reprinted with permission from [3]. Copyright 2012 AIP Publishing LLC.

 

However, experimentally obtained IBSCs suffer from a significant voltage loss resulting in lower than predicted theoretical conversion efficiency due to the short lifetime of electrons in the intermediate states. The short lifetime is caused by fast radiative and non-radiative recombination of carriers that occurs before the second photon can be absorbed. To achieve a long carrier lifetime of electrons in the IB, the authors suggest the introduction of a non-emissive (optically decoupled from the valance band (VB) [3]) “ratchet band (RB)” at an energy interval ΔE below the IB (shown in Fig. 1(b)). If there is fast thermal transition between the IB and the ratchet band, the photo-excited electrons in the IB rapidly relax into the RB where the lifetime of the carriers can be very long given that the RB is optically isolated from the VB. The increase in lifetime of the electrons enhances the probability of the second optical excitation process from the RB to the CB and increases the IB-CB generation rate. At the same time, the recombination rate of the electrons from the IB to the VB depends on the population in the IB. The presence of the RB reduces the population of carriers in the IB and the same the recombination rate leading to the increase of the photocurrent of the solar cell and its higher efficiency.

Figure 2 of Anna's blog

Fig. 2. Efficiency limit of photon ratchet IBSC of various concentrations as a function of ΔE. Efficiency at ΔE=0 corresponds to conventional IBSCs. Reprinted with permission from [3]. Copyright 2012 AIP Publishing LLC.

Authors calculate the globally optimised limiting efficiency of the photon ratchet IBSC as a function of the energy difference ΔE between the IB and RB. These dependencies are plotted for three solar concentrations in Fig. 2. Even though electrons lose the energy ΔE by transitioning from the IB to the RB, an increase in efficiency is visible as ΔE is increased. At the same time, the presence of the ratchet increases the below-bandgap and thermalization losses, but the associated efficiency gain through reduction in recombination is even larger. At 1 sun illumination, the efficiency of the IBSC is increased from 46.8% (ΔE = 0, conventional IBSC) to 48.5% with a photon ratchet at ΔE = 270 meV. At full concentration however, the introduction of the loss due to the presence of the ratchet band is not compensated by any other mechanism, leading to a decreased efficiency of the IBSC with the RB as compared to the standard IB cell (ΔE = 0).

Although it seems that the implementation of the photon ratchet IBSC is going to be challenging, I think that this concept is very interesting. Authors suggest that the RB can be built out states of indirect bandgap semiconductor separated in momentum space from the IB. Electrons would be first excited into a direct IB state, followed by a relaxation down through phonon emission to an indirect photon ratchet state, which is at a lower energy and separated by momentum k from the IB state, as well as the top of the VB.

Anna Trojnar's picture

 

-Anna Trojnar, Ph.D

Postdoctoral Fellow

Sunlab, University of Ottawa

 

[1] A. Marti, L. Cuadra, A. Luque, “Quantum dot intermediate band solar cell” Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference, p940 (2000).

[2] A. Luque and A. Martí, “Increasing the efficiency of ideal solar cells by photon induced transitions at intermediate levels”, Phys. Rev. Lett. vol. 78, p5014 (1997).

[3] M. Yoshida, N. J. Ekins-Daukes, D. J. Farrell, C. C. Phillips, “Photon ratchet intermediate band solar cells,” Appl. Phys. Lett. vol. 100, p263902 (2012)

As Ontario’s flagship renewable energy (RE) incentive program, referred to as the Feed-in Tariff (FIT), enters its third review, it is an appropriate point to assess several recent political and policy changes which have implications for the next iteration of RE incentives. In my previous blog, I wrote about the challenges facing Photovoltaics (PV) with respect to the World Trade Organization’s (WTO) initial ruling against Ontario’s domestic content requirements, growing economic turbulence in the RE sector, political adjustments within the provincial Liberal party  as well as other industrial and policy factors that have created uncertainty surrounding the future deployment and development of PV in Ontario. These events have had lasting impacts on the prospects of PV and continue to influence future policy engagement. In conjunction with prior developments, there are new pressures and policy changes which will have serious implications for PV. Do these changes point to positive change for the future of PV?

Foremost among these pressures is the fallout around the WTO decision. In May 2013, the final ruling by the WTO stated that Ontario’s RE policy framework was in violation of international trade law[i]. The decision established that the domestic content requirement, which requires that developers source a certain percentage of RE system components from Ontario companies in order to be eligible for FIT incentives, contravenes international trade agreements. Without protection from international competition, PV companies who have invested in Ontario face an uncertain future. Will PV panel manufacturers be able to compete with Asian firms? Which parts of the PV value chain will Ontario firms occupy? Will we purchase technology from overseas and focus primarily on project installation? These are just some of the questions left unanswered as the government begins to reinvent the FIT.

The provincial government has already communicated significant changes to the FIT, which may portent further revisions presently being contemplated. In June 2013, the government announced that large RE projects (>500 kW) would no longer fall under the FIT mechanism[ii]. Instead, these projects would be contracted using a competitive procurement process. The details of this process have yet to be articulated. Moreover, the annual cap for FIT contracts has been reduced from 250 MW to 200 MW[iii]. Aside from the FIT, the political administration has also renegotiated its deal to procure a significant quantity of RE from Samsung, cutting the contract from 2,500 MW down to 1,369 MW[iv]. From this, it would appear that a deliberate effort is being made to slow further RE procurement and deployment in the province.

Political pressures are also quite notable. First there is the continued uncertainty arising from a minority government situation, where opposing parties have stated they would either abandon[v] or seriously redesign[vi] RE policies. Second, controversial gas plant cancellations continue to plague the governing party, casting shadows over the energy file and the commitment to RE deployment[vii]. Lastly, and perhaps most importantly, there are still many unanswered questions regarding the future of nuclear energy in the province[viii]. If Ontario commits to build new nuclear reactors, there is little impetus to invest in RE and efficiency.

Together, the above factors indicate that there is increasing uncertainty surrounding the RE sector in the province. Recent developments suggest that Ontario is veering away from its commitment to an economy and energy system based on RE. So, the worst may have yet to come for PV in Ontario.

Danny Rosenbloom

Daniel Rosenbloom
Ph.D Candidate

Carleton University


My name is Bruno and I’m a postdoctoral fellow in the group of Michel Côté  at the University of Montréal. Our group focuses on developing “beyond ab initio” numerical methods in order to model organic molecules, polymers and interfaces for applications in organic photovoltaics.

Organic materials offer great promises for photovoltaic applications, mainly because they would be very cheap to produce. Indeed, we are constantly surrounded by plastics of various kinds, so there already exists a large chemical industry that can handle vats of the stuff. Wouldn’t it be great if you could just buy 100 square meters of rolled up photovoltaic plastic films at a local hardware store, unfurl it on the roof at home and get some of the Sun’s sweet power for (almost) free?

Well that’s still science fiction at this point but our group’s goal is to help make it happen. There are very many possible organic compounds and polymers,and exponentially more possible combinations which could do the trick. It’s like looking for a needle in a haystack, really. My colleagues in organic chemistry tell me it takes a student one year to create a new compound; that’s a lot of resources lost if the compound turns out to be a dud. Chemists of course have great intuition, and can discard some unlikely candidates right away. However, it is not always so obvious from the start whether a given molecule will have all the right properties for photovoltaic applications; that’s where we come in.

It is much cheaper to simulate numerically the properties of a new candidate molecule than to actually cook it in the lab and then measure its properties. The theory behind those models isn’t perfect of course, and experimental measurements have the last word, but efficient simulation tools can allow us to scan large databases of candidates and discard the crazies, leaving only probable candidates for further investigation. The rub lies in having an algorithm which is precise
enough to be useful, but runs fast enough so we can simulate those large organic molecules! We have been working hard on developing such a method, and we hope
to produce exciting results soon!

Colleagues and I visited the group of Professor Holdcroft at Simon Fraser in Vancouver at the beginning of April (see our photojournal of the trip here ). From our very engaging discussions with Professor Holdcroft and his students emerged a fact well known to experimentalists, but perhaps sometimes glossed over by ab initio-ists such as myself: morphology is critical to good performance! Indeed, photovoltaic devices rely on bulk heterojunctions to harvest the Sun’s energy: an electron donor compound is mixed with an electron acceptor (often PCBM), forming an intricate network of domains at whose interfaces excitons must dissociate and through which charge carriers must percolate. Obviously the shape, size and orientations of these domains will affect device performance greatly, and knowing the energy levels of single molecules are not sufficient to fully characterize the performance one can hope to reach with a given device. Furthermore, the ideal material should self-assemble to the optimal geometry without excessive human intervention; the more complicated the steps that are needed, the higher the cost of the final product!

Therein lies a bit of a terra incognita for me. I think we can do a great job at predicting the properties of a single molecule or polymer, but how can we scale up our modeling, and use the appropriate microscopic information to predict the behavior of mesoscopic (or even macroscopic) devices? This is a topic I want to know more about! Thanks for reading, and it was great to see you all in Hamilton at the 2013 Next Generation Solar conference!

Bruno Rousseau

-Bruno Rousseau

Postdoctoral Fellow

Department of Physics, University of Montreal

I recently attended the 2013 Materials Research Society’s (MRS) Spring Meeting from April 1st  to 5th in San Francisco, California. The MRS brings together members of industry, academia, and government to discuss the latest in materials research across a wide variety of disciplines. There were 56 parallel technical sessions, an exhibit, and a wide variety of tutorial sessions taught by leading scientists and engineers.  I presented a poster entitled, “Flux engineering for height dependent morphological control of branched nanowires” in a section focused on nanostructured semiconductors and nanotechnology. I attended talks primarily focused on nanowire growth and applications. Numerous talks focused on the use of nanowires in photovoltaic devices that I believe are of interest to the Canadian Photovoltaic Innovation Network.  Here I will briefly discuss a couple of highlights.

Results from a paper recently published in Science detailing high performance solar cells consisting of nanowire arrays were presented by a member of The Nanostructure Consortium at Lund University in Sweden.1  P-i-n junction indium phosphide nanowire arrays were employed in the devices, resulting in a maximal efficiency of 13.8% at one sun. InP nanowires have extremely low surface recombination velocities, removing the need for surface passivation as required by nanowire composed of alternative materials (such as Si). Interestingly, the devices exhibited short circuit current densities at 83% of the highest performance planar InP cells, while only covering 12% of the surface (as compared to 100% surface coverage in planar devices). The authors concluded that ray optics is not suitable to model the interaction of light with subwavelength nanostructures due to resonant light trapping. As a result, the authors suggested that nanowire PV devices could potentially reduce the amount of material required to fabricate cells by producing photocurrents comparable to planar devices.

An interesting talk entitled, “Band-gap and structural engineering of semiconductor metal oxides for solar energy conversion,” described the use of 1-D nanostructures (nanowires) to serve as direct pathways for charge extraction in dye-sensitized solar cells (DSSCs).2 In this work, zinc oxide (ZnO) nanowires were used due to their high electron mobility. In a typical nanoparticle film, electrons undergo “zig-zag” transport, increasing transport time and the probability for recombination or trapping. As a result, much of the generated charge carriers are not collected, leading to low performance. Direct “straight-line” conductive pathways are provided for electrons by implanting ZnO nanowires into the nanoparticle film. As a result, charge collection efficiency is significantly improved.  The implementation of ZnO nanowires improved efficiency in DSSC devices by 26.9% in the best performing device.

References

1. Wallentin, J. et al. Science 339, 1057, (2013).

2. Bai, Y. et al. Advanced Materials 24, 5850, (2012).

Allan Beaudry

-Allan Beaudry

Ph.D Candidate, Year 2

Electrical and Computer Engineering Department, University of Alberta

We are constantly inundated with projections, estimates, and forecasts of our future global and photovoltaic (PV) energy requirements. How much energy will we need by 2050? How much of our energy should come from PV? How much PV capacity can we install by 2020? Will that be enough?

I thought it would be interesting to see how we’ve done on our last decade of projections for global PV installations. The European Photovoltaic Industry Association (EPIA) is among various organizations that project and report the status of the PV market. From a series of EPIA’s Solar Generation (SG) reports ranging from SG1 (2001) to SG6 (2011) I looked at year-over-year projections for total global installed PV capacity, and plotted them alongside the actual installed values (see Figure 1).

Figure 1 for Ryan Tucker's blog

Figure 1 Cumulative installed photovoltaic capacity values and estimates from several EPIA reports.

It turns out that we’ve consistently beat the projections by large margins. In fact, the 2010 installed value (>39 GW) is more than a factor of three higher than the 2001 projections for that year (~13 GW). We can see from the plot in logarithmic scale that the installed capacity keeps jumping off of the exponential prediction curves.

The industry has made well on its promises. We must realize that the solar industry is in an enormous state of growth, but only because we are so far behind. This exponential growth is not sustainable for the industry. Certainly there has been amazing growth in the past decade, and we hope that this trend will continue for the following decade or two. Beyond that, let’s just hope that the total capacity is a significant portion of the global energy supply, and the industry can happily transition into a more steady growth state. In the meantime, I’m happy to take every megawatt of PV that we can get!

 

Ryan Tucker

-Ryan Tucker

Ph.D Candidate, Year 4

Department of Electrical Engineering, University of Alberta

 

Panelists:

David Brochu – Vice President Development, North America, Recurrent Energy

F. Michael Cleland – Nexen Executive in Residence, Canada West Fountation

Senator Grant Mitchell – Vice Char, Standing Committee on Energy, the Environment and Natural Resources, Liberal Senator, Alberta, Senate of Canada

Jon Kieran – Director, Development, EDF, EN Canada Inc.

Christian Vachon – President, Enerconcept Technologies

CanSIA concluded with a panel discussion on the development of a national energy strategy. The panelists consisted of David Brochu of Recurrent Energy, F. Michael Cleland of Nexen, Senator Grant Mitchell, Jon Kieran of EDF EN and Christian Vachon of Enerconcept. All members of the panel had the opportunity to express their opinions on how we need to proceed as a nation towards developing our energy strategy.

Four years ago Canada entered the Kyoto protocol in an effort to curb human-generated green house gas (GHG) emissions. Entering Kyoto was a move in the right direction for Canada, but ultimately we developed an unrealistic plan that we could not uphold. After failing to meet target reductions of GHG’s, Canada withdrew from the Kyoto protocol at the end of 2011. Canada needs to learn from its mistakes and work on developing a national energy strategy that will benefit Canadians.

What would a national energy strategy look like, and how would we get there? We could start by increasing engagement and advocation for development of an energy strategy for Canada. Promotion of open discussion to define what is important to Canadians in a energy strategy needs to occur. Why do we need a national energy strategy?  How much do we focus on making renewables a central part of our energy policy? Should we be putting a price on carbon, and would a carbon tax hurt Canada? How can we focus on the longevity and long term views of an energy strategy for Canada? There are many questions to be answered with no readily apparent solutions.

Where do solar energy and other alternative energy sources fit within Canada’s national energy strategy? Following the success of the feed in tariff (FIT) and micro-FIT programs, Canada has developed FIT 2.0  which will put another 160MW of solar energy online. The arrival of FIT 2.0 was not a surprise, but we will likely be seeing less government subsidy of solar projects. We cannot be reliant on a technology that requires subsidy to be sustainable. Fortunately, we have already seen instances where solar energy can be produced at grid parity. With the dropping prices of solar energy and the ever escalating price of non-renewable energies, it is essential for solar to be a large part of Canada’s energy strategy. With the help of the FIT programs, Canada aims to be recognized as a leader in the installation and manufacturing of solar modules.

Canada needs to sculpt an energy strategy that can drive our economy, promoting growth in an underdeveloped sector. An energy strategy that will advance job growth within Canada, and ultimately will lead to a more sustainable country.

 

-Matthew Schuster

M.ASc

Queens University

Thanks to the Photovoltaic Innovation Network, I participated in Solar Canada 2012 in Toronto, Ontario. This conference/exhibition is the largest national solar event in Canada, and is hosted by the Canadian Solar Industry Association (CanSIA). This year the event was quite large, in part due to the fact that it was CanSIA’s 20th anniversary.

In this conference, I participated in some talks and visited some booths; one of the talks that was really interesting to me was about Solar thermal, Geo-thermal and the opportunity to integrate these two technologies together. Solar thermal installations consist of a solar thermal collector on the roof, a control unit with a pump and a potable water storage tank. The collector absorbs the light from the sun and converts it into heat. This heat is transferred to a liquid which circulates through the collector and down into the solar storage tank (fig-1). There are a lot of solar thermal projects within Canada (as they can easily deployed, even in residential areas), but one of the biggest is at Oxford Gardens retirement home in Woodstock, Ontario. This solar thermal project is saving on air conditioning costs by up to 40%, or approximately $20,000 per year; for heat savings, up to 60% or approximately $40,000 per year, according to Suni Ball from Proterra Solar[1].

 

dummypic1

    A geothermal heat pump, ground source heat pump (GSHP), or ground heat pump is a central heating and/or cooling system that pumps heat to or from the ground. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). Heat pumps provide winter heating by extracting heat from a source and transferring it into a building. In the summer, the process can be reversed so the heat pump extracts heat from the building and transfers it to the ground. Transferring heat to a cooler space takes less energy, so the cooling efficiency of the heat pump gains benefits from the lower ground temperature (fig-2).

 

dummypic1

The combination of these two systems has many benefits [2]:

-Both systems don’t use fossil fuels at the point of use

-Geothermal is the backup for the solar thermal while the Geo-thermal can also provide cooling.

-Large flexibility in the heating appliances that can be used with both systems.

-Using the geothermal loop field as a storage tank to absorb the excess solar energy in the summer.  This advantage allows you to oversize the solar thermal system and increase the solar thermal contribution to the winter heating.

A study has been done [3] for the viability of a combined system in Milton, Ontario. This study shows that a combined system is feasible for space conditioning. For the house in this study, the seasonal solar thermal energy storage in the ground was sufficient to offset the large amount of Geo-thermal pump system length that would have been required in conventional systems. They showed that the economic benefit of such system depends on climate, as well as borehole drilling cost.

To conclude, a hybrid Solar-Geo-thermal system could be an outstanding solution to the high demand of energy in today’s world. It has a lot of benefits like sustainability, being clean (non-polluting) and having the ability to work all year round. Another important benefit is the possibility of using this system for all kinds of applications such as residential, commercial and industrial.

Farbod Ghods-Farbod Ghods

Ph.D Candidate, 1st Year

Department of Engineering Physics

McMaster University

References

[1]- http://oxfordgardenssolarproject.com

[2]- http://www.dma-eng.com/

[3]- Rad et al, COMBINED SOLAR THERMAL AND GROUND SOURCE HEAT PUMP SYSTEM, Eleventh International IBPSA conference, Glasgow, Scotland, July 2009.

Chair
Ian MacLellan, President and CEO, Ubiquity Solar Inc.
Panelists
Nic Morgan
, Co-founder and VP Business Development, Morgan Solar
Jan Dressel, President & Managing Director, SPARQ Systems Inc
Ray Morgan, Director Outreach, PV/Solar & Semiconductor, SEMI Americas
Rafael Kleiman, Professor, Director, McMaster University
Clemens van Zeyl, CEO & Co-Founder, ARDA Power Inc.

Picture from Ahmed's blog

 

An interesting panel discussion took place on innovation. The panel discussed the meaning of innovation from different points of view. Everyone agreed that Solar is happening faster than everyone expected. In 2001, it was predicted that the world market for new installations in 2010 would be 2.8GW. In 2006, the prediction was increased to 5.5GW. The actual result for new installations in 2010 was 16.8GW. According to PV experience curve, PV module price is estimated to be as low as $0.15/W by 2050. For more information, check out the white paper issued by CanSIA here.

Innovation trends for PV:

  • Silicon is and will continue to be the main PV technology, giving a hard time to thin film technology.
  • Organic PV might be a player in 20-30 years for specific applications
  • Improving reliability in manufacturing yield and PV life time
  • Integration of solar systems in commercial buildings by removing the inverter, ie: DC power lines as most instruments work on DC.

Finally, to go the last mile in innovation, it has to be on the system level!

Ahmed GabrAhmed Gabr

PhD Candidate, 2nd Year

SUNLAB – University of Ottawa