Renewable Solutions: Novel Ideas

As previously discussed, energy storage for renewables is important, especially when relying on them for a greater proportion of global energy production. The innate unpredictability of natural renewable energy resources (wind, sun, river discharge, tides) makes energy storage facilities vital for supplying constant levels of electricity to our constant (exploitative) demand.

The most wide spread and popular energy storage technologies include (taken from Perna et al., 2015):

• Electrochemical batteries
• Supercapacitors
• Thermal-storage materials
• Flywheels
• Pumped hydro reservoirs
• Superconducting magnetic energy storage
• Chemical (hydrogen, synthetic natural gas, etc.) storage
• Compressed air energy storage (CAES and ACAES)

Each method is suited to different applications and vary in stored capacity and efficiency, and discharge rate. Electrochemical batteries can be highly efficient and store large amounts of energy, but have limited life cycles and discharge stored electricity at a slow rate (Perna et al., 2015). CAES systems similarly have a high efficiency, but contrastingly have longer life cycles and can store a varied amount of electricity, depending on the built capacity. Hydrogen-based energy storage systems (water electrolysis) tend to have lower efficiencies, but has a high storage of energy per mass, whilst having a long life cycle (Perna et al. 2015). However, this post will look at some of the more interesting solutions published recently!

Perna (et al., 2015) undertook an interesting study looking at how hydrogen-based energy storage systems could be integrated with biomass powerplants, making the biomass production more efficient. Overall, electrical efficiencies of the integrated systems ranged between 40-43%. To me this is incredibly low, but compared against incineration or biomass gasification (which has an efficiency of 20-24%), efficiency levels look great! Furthermore, integration provides a demand for electricity when consumer demand is low, reducing electrical fluctuations across the supply networks and improving reliability!

Another unique and new means of storing energy is the use of using liquid carbon dioxide. Wang (et al., 2015) investigated different systems by which to pressurise liquid carbon dioxide. During off-peak or low demand periods, liquid carbon dioxide is pumped from one tank to another through a series of compressors (consuming excess power). When additional power is required, the pressurised liquid carbon dioxide is released through turbines to generate electricity. Heat exchangers are cooled using oil, and the heated oil is used as a secondary source of electrical generation, heating water to turn turbines. 

Figure 1: Comparison of methods of energy storage with
RTE (Round Trip Efficiency - total efficiency) and EVR (energy:volume ratio) (Wang et al., 2015)

Wang's paper explores a number of schematics, suggesting that the improvement of thermal energy storage (heated oil) can improve overall efficiency (RTE) to 56.7%. Furthermore, the energy to volume ratio (EVR) is a reasonable 36.kWh/m3, making liquid carbon dioxide energy storage a more efficient (in terms of volume to energy ratio) means of storing energy compared to CAES and Pumped hydroelectric reservoirs (Figure 1).

When combined with storage mediums, renewables can be very useful. A mixture of various renewable resources combined with storage capacities mitigates reliability issues. To wrap up this post, I have found an exciting article which provides a model for a completely renewable-powered city.

Richardson and Harvey (2015) have modelled the renewable potential surrounding Ontario, Canada, investigating what would be required to move from conventional fuels to a fully renewable system which includes pumped hydroelectrical and battery storage. The model results aren't particularly detailed, as rough estimates are used based on existing literature or known specifications. However they optimistically conclude that Ontario could move towards a renewable-based electrical generation system which is reliable and a renewable-fuelled city "can be maintained without excessive generation costs". The idea, they explain, is technically feasible, however there are issues surrounding potential demand fluctuations with electrification of transportation, which could prove to be problematic.

The results from all 3 studies are optimistic. There are an abundance of methods and means to cope and sustain our excessive demands for energy, and when scaled up to a city-wide model, the level of technology we currently are at seems to prove that we can indeed live sustainably (whist still exploiting the abundance of energy)!
As a side note, Richardson and Harvey do note that a change in behaviours would probably help to make renewable-based cities a reality for more parts of the world. I completely agree with this, but that conversation is for another blog!

Bad Coal, Good Alternatives

Coal is an important resource and is predicted to become of increasing importance in new energy production. In light of COP21 and a global push to keep carbon emissions to a minimum this is an important issue.

Coal has become a staple across the energy landscape (Source) 

Analysis which was presented at COP21 suggests that if all coal plants planned to be built by 2030 are built, coal emissions would increase by 400%. Even with no additional coal plant construction, predicted emissions from coal are 150% too high to keep global temperatures below 2 degrees.

Calculated carbon increase from analysis results (Source)

This is a slight issue... And considering temperatures have already gone up by an average of 1 degree since pre-industrial times, the threshold of 2 degree temperature rise is becoming more and more problematic.

For many countries, providing their citizens with electricity is of far more importance than cutting carbon emissions, even for those countries may have agreed Intended Nationally Determined Contributions (to cutting carbon), or INDCs. Ultimately, this can lead to a number of issues which will impact the final result of COP21: increases in carbon emissions and displacement of renewable energy. These countries, many of which are developing, such as India and China, are still investing in renewable energy sources, but the uptake, cost and generation is too small to be effective in bringing electricity to the masses.

So how do we approach coal? I believe we need to appreciate it is a cheap, very widely recognised and used technology globally. What can be changed is the types of coal and the technology used within coal plants to mitigate the issues. Furthermore, pushing cleaner technologies, such as gas may be a more suitable, cleaner and (potentially) more efficient solution (and one which will be dominating the UK energy space for the next 20 years).

Technology:

Carbon Capture and Storage (CCS)? I feel CCS is a utopian idea which is and will continue to be only suitable in a hypothetical world. CCS has had has limited testing. It provides us with an additional carbon sink. But continues to allow our exploitative approach to carbon for energy. There are also risks to CCS. The principle is to pump the carbon back into old oil fields, but contamination and leakages could present themselves as a large issue.

Renewables? Could be a solution for developing nations. Funding must be available, however renewables do provide grassroots-scale energy production without the need for expensive infrastructure development - an especially important issue in fast growing cities.

These two latter aspects are items I will look at and investigate in my next two blogs: carbon sinks (afforestation) and renewable production (solar farms) - how can our use of the sun and trees mitigate against our exploitative use of electricity?

Edit: the second photo was added at a later date to provide some visualisation to the figures discussed above

Positive energy crisis?

With our life-or-death reliance on energy, it might come as a surprise that the UK is struggling. For the first time, next year, Britain will not have enough "dispatchable energy generation capacity" (essentially, power plants which can be switched off and on to meet excess demand, contrasted against wind and solar energy which is a non-reliable, non-programmable energy source). 

Is this our future? (Source)

Over the last 5 years, Britain has lost 20% of its baseload dispatchable energy and have no replacements planned in the near, with the further hope of shutting down the remaining 13 coal power stations, which generate a third of the UK's energy. This would mean the potential to have power-cuts!

From this point we can go two ways. We can build cheaper, coal-powered stations and provide us with the energy we need in a short period of time. 

Alternatively, this gives us the opportunity to invest in cleaner more energy and carbon efficient fuels. The UK has a great opportunity to move into gas-fired and nuclear power stations, cleaner fuels with less environmental impact. A great blog on the intricacies of nuclear can be found (here). At this point, most people would say, "oh, but why not invest into wind and solar?". Well the government advocates no longer relying on subsidies, urging the private sector to take the burden of the investment. 

Maybe it's a good move? Only time will tell!

Natural Exploitation

Unlike plants, which approach resource exploitation as a 'dominate or die' principle, humans are less prone to that way of thinking. Natural resources, and most importantly fossil products are highly sought after, and there has been a various research and theoretical frameworks developed to understand exploitation and humans. Some of the theoretical frameworks developed are useful, others merely seek to understand the interactions between humans and resources in a shallow network-y way. But in a climate change paradigm, the interactions are not the most important part. What impact does our exploitation of fossil resources have on the environment?

One of the key impacts of fossil resource exploitation is their greenhouse gas emissions. I won't insult anyone's intelligence by explaining what greenhouse gasses are, which gasses are involved (water vapour is a greenhouse gas also) or the impacts of greenhouse gasses; instead I will allow BBC Bitesize to insult you instead!

The coloured portions of this map identify 86%
of carbon emissions, globally (Source)

An optimistic report produced by the International Energy Agency (IEA), and reflected by a report recently released by BP suggests that global carbon dioxide emissions from energy grew at their slowest rate since 1998. All this occurred whilst global economies grew, indicating a global investment in mitigation solutions against high polluting energy fuels. Of all energy sources, however, oil is still a global leader in production of energy, supplying 32.6% of the world's power.

I will explore the issues around energy production, as well as looking at low polluting methods of energy production and the issues associated with global energy understandings and low pollution energy generation methods. The impact of energy cannot be ignored in modern global environmental change.