3 item(s) found.

Transport Trade-offs

Transport Trade-offs

The Magic Nexus team

Transportation is an important issue for the study of the nexus. It is both the target of innovative solutions that may help solve the challenges of energy and climate, and the source of challenges and trade-offs in sustainability governance. An example of innovative solutions are electric vehicles that promise an alternative to fossil fuel-based transport. On the other hand, biofuels are an example of an innovation that initially seemed to lead to more sustainable energy sourcing, but has created new challenges for land use in agriculture and has fallen short of expectations of reduced pollution and energy provision. In this issue, we take a closer look at both examples and we engage with the newly emerging debates about car sharing and the sharing economy.

Starting with biofuels, our first article tackles the question: do biofuels really produce less greenhouse gas (GHG) emissions than fossil fuels? Bunyod Holmatov takes us through the intricacies of GHG accounting and explains that emissions vary according to the type of biofuel, to production routes and steps, and to the type of GHG considered. Overall, GHG accounting is a challenging task, and Holmatov advises policy makers to measure twice.

The research team based in the Autonomous University of Barcelona continues the discussion by showing that statistics about biofuels vary considerably due to differences in accounting methods between European countries and issues of double accounting. Overall, there is no clear evidence base for policies, which is reflected in the ambiguous role of biofuels in the European policy. Biofuels were at first seen as a greener alternative to fossil fuels and later criticised for the indirect land use change they induced, as in the case of palm oil.

Wrapping up the discussion, Maddalena Ripa, Mario Giampietro and Juan Jose Cadillo Benalcazar explain the many concerns related to biofuels, which range from Europe’s dependence on imports to the low energy return on energy investment, the challenge of fuelling aviation with biofuels, the lack of technological infrastructure to produce biofuels in Europe, and the general lack of transparency surrounding biofuels in policy. Are biofuels a matter of concern rather than a solution?

In our fourth article, Louisa Di Felice takes up the example of electric vehicles. Electric vehicles are not as new as one may think: they were first commercialised in the 1880s. So why has this “innovation” been so slow to deliver on its promises? The article explains some of the drawbacks of electric vehicles, such as the sourcing of lithium for batteries and the underwhelming recycling rates. More importantly, Di Felice argues that sustainability necessitates behavioural change rather than technologies that enable unsustainable practices to persist.

Behavioural change is not without its uncertainties. Roberta Siciliano closes the issue with a discussion of car sharing, which was expected to deliver a sharing economy through which less resources would be used, but due to the success of its business model has created a new market and new business possibilities that induce more, not less, consumption. Siciliano warns that sustainability is not about finding “silver bullets”. What is needed is a collective rethinking of mobility.

Desalination is a viable nexus technology: but local conditions are key

Desalination is a viable nexus technology: but local conditions are key

Juan A. de La Fuente and Baltasar Peñate

The world population is expected to increase from the current 8.5 billion to 11.2 billion by 2100 (World Population Prospects, United Nations 2017). By 2050, global demand for energy will nearly double, while water demand is set to increase by over 50%. To overcome the increasing constraints the world faces, we need to rethink how we produce and consume energy in relation to the water sector.

The authorities responsible for water and energy are generally separated. Each has its own priorities and there seems to be little incentive to collaborate in the planning and development of new policies. At the same time, the water and energy sectors have always operated independently and there may be some resistance to a better integration of both sectors. Often, studies on the interconnection between water and energy have been initiated and driven by specific local circumstances, such as water and energy crises.

Seawater desalination is an important option for addressing the world's water supply challenges, but current desalination plants use huge quantities of energy causing several environmental issues. The energy intensity of desalination processes has dramatically decreased over the past 30 years, from slightly more than 15 kWh/m3 in the 1970s to approximately 2.5 kWh/m3 today thanks in large part to reverse osmosis (RO) technology improvements. Still, several physical constraints limit the ability to reduce the energy intensity of RO much further. This means that energy efficiency in RO has almost reached its biophysical limits.  

Brine discharge into the sea can have a negative environmental effect on the marine ecosystems due to its high salt concentration and other chemicals. Devices like Venturi diffusers for brine discharge can be used to improve the dilution process and reduce their environmental impact. It has been shown that the capacity to improve the dilution of Venturi system is greater than 2.3 times the dilution obtained with conventional diffusers. Another option could be the valorisation of brine, by using it for the culture of the microalgaes for the production of molecules such as β-carotene and polyunsaturated acids. The biomass obtained can be used in animal nutrition and Nutraceutics.

It is very likely that the water issue will be considered, like fossil energy resources, to be one of the determining factors of world stability. Desalination processes involve a recurrent energy expense which few of the water-scarce areas of the world can afford. Even if oil were much more widely available, could we afford to burn it in such a manner so as to provide everyone with fresh water? Given the current understanding of the greenhouse effect and the importance of carbon dioxide levels in the atmosphere, environmental pollution caused by burning fossil fuels for desalination is a major concern.

Renewable energy (RES) technologies, mostly solar and wind energy systems, can provide access to a cost-effective, secure and environmentally sustainable supply of energy that can be used for water desalination. As RES technologies continue to improve, and as freshwater becomes scarce and fossil fuel energy prices rise, utilising RES for desalination becomes more viable economically. RES may provide water desalination cost reductions due to lower greenhouse gas emissions. For example, a seawater RO desalination system operating on traditional fossil fuel-based energy sources produces 1.78 kg and 4.05 g of CO2 and NOx per 1 m3 of desalted water, which can be reduced to 0.6 kg/m3 – 0.1 kg/m3 and 1.8 kg/m3 – 0.4 kg/m3, respectively, with electricity generated from wind or solar energy  (Raluy RG, Serra L, Uche J. 2005. Life cycle assessment of desalination technologies integrated with renewable energies. Desalination 183(1–3):81–93).

On the other hand, the role that desalination could play in the integration of electricity produced by renewable sources in the electricity grid is also an interesting topic.

The major constraint on increasing penetration of RES is their availability and intermittency, which can be addressed through using energy storage or smart control, when available, to balance renewable energy generation with energy demand.

The Canary Islands archipelago in Spain is a perfect example of how a region with water shortage and presence of RES resources has alleviated its water scarcity problem using desalination technologies, exploiting in turn the sun and wind resources available in the area.

The water – energy nexus has been one of the key R&D lines of the Canary Islands Institute of Technology (ITC). The ITC has developed and tested prototypes of different renewable energy driven desalination systems, operating in off-grid mode, since 1996. The ITC facilities in Pozo Izquierdo (Gran Canaria Island) are an ideal platform for testing RES desalination systems thanks to the excellent local conditions: direct access to seawater, annual average wind speed of 8 m/s, average daily solar radiation of 6 kWh/m2. Up to 18 different combined systems of renewable energy generation and desalination processes have been tested at the ITC.

Depending on the local environmental conditions, regulation and policy, desalination is a viable technology where RES resources are readily available. With planning and an adequate policy, desalination should be an alternative water resource. However, the energy dependence and the relatively high water cost must be analysed on a case by case basis before proposing specific arrangements.

Is renewable energy efficient?

28 September 2017

Is renewable energy efficient?

Louisa Jane Di Felice

Renewable energy and efficiency are both essential to meet the EU’s sustainability goals, but synergies and trade-offs between the two measures are under-studied.

The EU 2050 Energy Strategy, released in 2011, identified four pillars needed to reach a sustainable energy system: energy efficiency, renewable energy, nuclear energy and carbon capture and storage. Across other EU strategies and communications, energy efficiency and renewable energy are predominant: on one hand, similar targets are set for both – see, for example, the 2020 Energy Strategy, calling for a 20% increase in both renewable energy and efficiency; on the other, they are both seen as measures needed to reach similar goals: namely, the reduction of greenhouse gases, with a 2020 target of 20%, and 30% by 2030.  However, the reduction of greenhouse gases isn’t the only motive behind renewables and efficiency, with renewable energy also increasing local production and security, and efficiency lowering energy bills.

With both measures dominating EU energy strategies, as well as national and regional energy plans, a question arises: do they contradict each other? While many studies focus on the importance of either one of the two, it is becoming apparent that, if the EU is to meet its ambitious targets, cross-checks among policies (both in the same realm, such as energy, and across different areas) are essential. The question, however, isn’t simple. An initial search on the synergies and trade-offs between renewables and efficiency yields diametrically different opinions.  Renewable energy supporters claim that renewable energy systems are vastly more efficient than their fossil-fuelled counterpart. They are not wrong: losses in the transformation from renewable energy sources to electricity are almost negligible, while thermal combustion plants have an inevitable heat loss, dictated by Carnot’s principle, limiting their conversion efficiency to a theoretical maximum, dependent on the maximum temperature at which the conversion process can operate. This is called thermal power generation efficiency. Coal plants, for example, have an average thermal efficiency ranging between 32% and 42%. Those who are more sceptical of renewable energy systems, however, argue that they are clearly less efficient than conventional power plants. Again, they are not wrong: wind turbines and solar panels operate at their full potential no more than 40% of the time, at best. Moreover, for the same electricity output, renewable energy generally requires more land, labour and investment.

So, who is right? To help untangle this mess, the first step is being able to compare renewable and non-renewable plants, and this in itself is not an easy task. Energy systems are composed of various phases, from extraction and transport of primary energy sources, to their conversion into fuels or electricity, to the transport of the former and the transmission and distribution of the latter leading, finally, to consumption. Each of these steps can be characterized by its own efficiency, and they are not easily comparable: an efficient coal plant is not the same as an efficient toaster. By harnessing primary energy sources when they are readily available, renewable energy systems avoid the steps of extraction and transportation of primary energy sources. Moreover, by relying on the conversion of renewable elements such as the sun and the wind, no resource is wasted in the process.  However, by comparing energy systems based on their structure, and not on their differences in output, only part of the picture is visible.

One of the main issues with renewable energy is intermittency. This means that while a wind turbine and a natural gas turbine may both produce a certain output of electricity, these two outputs are not the same: one can be controlled and used when needed during peak demand, while the other is produced randomly, regardless of demand curves. So to compare renewable and non-renewable systems, one has to start by assuming that they are producing the same output, and this means factoring storage into the equation. Only by considering the combined system of “renewable energy plant plus storage” can it then be compared to a conventional power plant, as both produce the same kind of electricity (the useful kind).

Quantifying the efficiency of energy storage, however, isn’t trivial. Similar to energy conversion, the efficiency of storage can be considered from different angles: one could, for example, check how much energy is lost in the storage cycle. Pumped hydro storage (PHS), where water is pumped to a high basin when electricity demand is low and then released during high demand, loses on average 25% of electricity over one cycle (also known as round-trip energy efficiency). But this isn’t really a loss, or we’d be mad to go through the cycle in the first place – the electricity pumped up-hill, and the portion that is lost in the process, is cheap electricity, generated at low demand times, while the one produced at a later stage is expensive, covering a much needed peak. They may both be electricity, but one is more valuable than the other. Lithium-ion batteries, another popular storage technology, have a higher round-trip energy efficiency of up to 90%. However, round-trip energy efficiency isn’t the only way to describe the efficiency of storage technologies. In 2014, researchers at Stanford University introduced the concept of “energy stored on investment” (ESOI), quantifying the storage potential of a technology against the storage capacity over its lifetime. In this case, PHS fares much better than chemical storage, with an ESOI of 210, over twenty times higher than that of lithium-ion batteries.

Quantifying the efficiency of renewable energy systems is no simple task. When it comes to discussing renewable and non-renewable energy systems, it is essential that they are compared against the same output. This means that storage cannot be left out of the equation. However, the question of what efficiency means in terms of storage is still under-explored, and better tools to assess storage technologies are needed, as renewable energy plays a greater role both in energy systems and in energy policies. It’s unclear whether renewable energy is more or less efficient, but accepting that there may not be exact answers to these kinds of questions, and that different framings and definitions of efficiency lead to different results, may be a necessary step forward in shaping comprehensive policies in times of uncertainty.