Team Energy Research Plan & Expert Questions
We attended a total of 3 workshops on the technologies that we considered most relevant to our task. The research below shows our results and understandings, upon which our design concepts in the next section are based.
Expert questions:
1. Solar cell:
Efficiency: Is solar energy more energy efficient than fossil fuels? Which PV cell is most cost-efficient?
Conservation: Are there technologies to store the energy for a 'rainy day'?
Surface: Is it possible to minimize the surface area required for a given amount of energy, so that we can mazimise the space available to us?
2. Fuel cell:
Storage: Is it safe to store hydrogen?
Efficiency: Is it more efficient than other kinds of renewable energy?
Weight: How about the weight of fuel cells, is it easy to move?
Cost: Is it expensive to build the infrastructure of fuel cells?
3. Batteries & E-Vehicles:
Capacity: What is the capacity of the batteries and how much power do they need?
Durability: How many times can the batteries be charged? How long can it be used?
Research (Zichuan)
FUEL CELLS
Background:
The concept of fuel cells was first introduced in 1838 by physicist William Grove (Sharaf and Orhan. 2014). For the next century, the research of fuel cells remained in the theory stage until the first alkaline fuel cell was created in 1959 (ibid). A fuel cell is a device that can change chemical energy into electricity. The basic structure of fuel cells is shown in the figure below.
Figure 1. The basic structure of fuel cells (Sharaf and Orhan. 2014).
Figure 2. The patents granted in the alternative energy sector between 2002 and 2017 (Sharaf and Orhan. 2014).
Theory:
The overall chemical reaction is:
and this reaction can be split into anodic reactions and cathodic reactions (Sharaf and Orhan. 2014 ).
Anodic:
Cathnodic:
On the anodic side, hydrogen is resolved into protons and electrons, which then go to the cathodic side and react with oxygen. This reaction enables the electrons to travel around the outside circuit, generating electricity. Overall, most of the chemical energy in the hydrogen is changed into electricity, the rest is wasted in the form of heat and there is no carbon emission.
Advantages:
- Fuel cells are a relatively efficient way of generating energy. In theory, the efficiency can reach more than 80%, and ITM (Interactive trading mode) claimed that the actual efficiency of fuel cell was between 60% and 80% (Jervis. 2015).
- The only by-product of the chemical reaction is water - there is no carbon emission during this process.
- The fuel cell is reliable because there are no moving parts, which means it can hardly be influenced by outside factors (Jervis. 2015)
- Using fuel cells can help to eliminate the economic dependence on other countries. Singapore is not rich in fossil fuels, but any country can produce energy using fuel cells as long as they have hydrogen, which can be generated by the process of electrolysis of water (Jervis. 2015).
Disadvantages:
- The cost of fuel cell is currently quite high. It takes 67 US dollars to generate one kilo watt of power (Jervis. 2015)
- The resource of fuel cells - namely the hydrogen - is hard to store. Since hydrogen has a very low density - about 14 times lower than air - it spreads easily into the air when leakages happen. This is both a waste and also very dangerous - burning impure hydrogen will cause explosions.
- Although hydrogen (H) is a common element on the earth, pure hydrogen (H2) does not occur naturally and must be produced manually. Generally, there are two ways to generate hydrogen (H2), one of which is steam reforming:
It takes 2 US dollars to generate 1 kilogram hydrogen. The price is reasonable, but carbon monoxide will be emitted during this process. The second way is by electrolysis of water, but the price of this process is 3 times that of the first approach (6 US dollars) (Jervis. 2015).
Research (Zihang&Gidon)
SOLAR CELLS
When we talk about solar cells, we think of it abstractly as a device that converts solar power to electricity. However, there are actually a variety types of solar cells, such as photo-voltaic cell and concentrated solar thermal plants, among others.
Photovoltaic cell
(http://www.pveducation.org/pvcdrom/solar-cell-operation/solar-cell-structure)
A photo-voltaic cell is a device that directly converts light into electricity. By the end of 2014, a total of 177 GW of PV cells had been installed around the world, making it one of the fastest growing energy resources in the world.
Photo-voltaic cells have a mature technique, which, as well as facilitating the solution different problems that can arise in the real world, also dramatically reduces the installation cost of PV cells. They have a relatively high energy conversion rate; somewhere between 14% and 19%. It is well known that solar energy is considered to be the cleanest energy, and has gained wide support with people. Data shows that 97% of people support energy produced by solar power, which gives it the highest support rate out of all the resources included in the survey.
Indeed, there are problems in adopting this technique, including the efficiency of electricity generation. Because the position of the sun changes depending on the time of year, or even the time of day, a tracker must be installed to keep the panel aligned with the sun, as maximum efficiency relies on the panel directly facing the sun. This installation of a tracker can prove complicated and expensive.
Concentrated Solar Power
Concentrated Solar Power (CSP) is another commonly implemented type of solar power technology. Report shows that an total of 3425 MW capacity was already installed in the end of 2013, and is predicted to reach 50 GW by 2032.
Concentrated solar thermal, compared to PV cells, is often much larger in scale due to its electricity generation mechanism. Solar power tower, one implementation of concentrated solar thermal, uses a large amount of heliostats (which consists of a mirror and a movable stand always direct the sun facing the sun) to reflect sunlight to the central power with receiver. The receiver then stores heat by melting salt with very high heat capacity, which then uses to boil water to drive turbines to generate electricity.
As all solar power generated electricity station, this technique benefits from several advantages including very lost marginal cost after the completion of station construction. Little amount of hazard waste produced in the electricity generation process, therefore more in the sense of a sustainable energy source. Regarding the cost of energy generation, report shows that the cost of electricity from CSP station is approximately same with that from natural gas, and lower than that from PV cell.5 It is obviously predictable as the improvement of CSP technology, and the declining amount of non-renewable energy source such as natural gas, a bright future for CSP electricity generation is foreseeable.
The drawback of this technique include the space and sunlight intensity requirement for the station. A large space is required for the implementation of the station, and also high sunlight intensity is required for the sake of efficiency. That is the exact reason why Ivanpah Solar Electric Generating System is built in a desert located in south east California.
References
1. 2014 Snapshot of Global PV Markets, IEA
2. Naggi, R. K. Solar Energy & Its Uses. New Delhi: Mahaveer & Sons, 2009. 7-11.
3. Global Citizen Reaction to the Fukushima Nuclear Plant Disaster, Ipsos
4. REN21, Renewables 2014: Global Status Report, 2014
5. Glennon, Robert and Reeves, Andrew M., Solar Energy's Cloudy Future (December 8, 2010). Arizona Journal of Environmental Law & Policy
Research (Chiara)
BATTERIES & E-VEHICLES (EV)
At the workshop about lithium batteries and e-vehicles (EV), presented by Donald Finegan from UCell, we looked into the system of EV and the motor powered by lithium batteries, as well as discussing the charging stations in terms of their efficiency and energy source, thus discussing the possible renewable resources that can be used under different conditions.
Lithium Batteries
These batteries work according to a chemical reaction that transfers lithium ions; the relevant feature is that this reaction can be reversed by recharging the battery through electricity.
This is where the sustainability concept gets misinterpreted as generating the required electricity is usually carried out through the use of fossil fuels. So although the technology of these batteries is very efficient and fits the purpose and use of e-vehicles, the energy required to recharge them as not yet met the purpose of sustainability. In figures this means that a standard car produces c.a. 150g of CO2 per km and powering a charging station with fossil fuel results in about 80g of CO2 per km. Clearly the environment is still negatively affected!
The batteries have an average lifetime of a couple a thousand recharging cycles, given that the charging happens at a slow rate (thus sparing the quality of the battery). In other terms domestic recharging should happen over night. Nonetheless the current technology provides the so called "Tesla Supercharging Points) where a battery can be recharged half way through in 20 min, this would be a solution under requiring conditions because the battery's lifetime decreases.
Electricity Production
In order to recharge the lithium batteries it is important to discuss the sustainability of the supply resources. For the conditions of Singapore, we have to take into account the high temperatures that can be reached in the country, as it is situated close to the Equator, because lithium batteries tend to perform less efficiently above 30°.
Nonetheless this characteristic can work in our advantage as we could transform the abundance of sun and heat in a "green" energy source. Solar power is also considered one of the most efficient renewable resources, although it requires surface for solar panels.
E-VEHICLES (EV)
At the workshop we looked into the mechanism of EV, in particular the Tesla model, as they tend to be the most competitive on the market, in some cases even against standard cars. The motor is powered by approximately 7000 lithium batteries (c.a.3.8V each) placed in modules and series, which take up most of the cost of the EV, but they practically are as user-friendly as standard cars. They have an autonomy of 480km (under specific driving conditions) before requiring a recharge, thus more than enough to cover the average distance travelled in Singapore in about 5 working days. The only big problem is the cost of these vehicles (as one lithium battery approximately costs 5 $), which are not quite yet affordable for the majority of the population, and the general uninformed attitude towards these technologies.
References
- Notes from energy workshop with Donald Finegan from UCell, 22.10.15
- Tool.globalcalculator.org,. 'The Global Calculator | Spreadsheet V.3.99.0'. N.p., 2015. Web. 23 Oct. 2015.
- YouTube,. 'A Reality Check On Renewables - David Mackay'. N.p., 2015. Web. 23 Oct. 2015.
- Teslamotors.com,. 'Tesla Motors | Premium Electric Vehicles'. N.p., 2015. Web. 23 Oct. 2015.
- Media.caranddriver.com,. N.p., 2015. Web. 23 Oct. 2015.
- Kwang, Kevin. 'Singapore Government Makes An E-Vehicle Push'. Businessweek.com. N.p., 2009. Web. 23 Oct. 2015.