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How far should renewable energy be transferred?
Eti
Posts: 107 XPRIZE
The variable nature of renewable energy is considered the primary challenge in its wide-scale adoption. Some places and seasons are more renewable energy-rich than others, yet renewable energy transfers remain a challenge.
When thinking of renewable energy transfers, what would be the ideal distance of energy transfer to increase the reliance on clean energy sources? What distances must be covered to increase energy resilience and reliable supply? Is there a scale that is detrimental to a successful transition to renewables? Are there distances that should be avoided - why?
When thinking of renewable energy transfers, what would be the ideal distance of energy transfer to increase the reliance on clean energy sources? What distances must be covered to increase energy resilience and reliable supply? Is there a scale that is detrimental to a successful transition to renewables? Are there distances that should be avoided - why?
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Comments
(For other readers, I posted an answer to some related questions from Eti here: https://community.xprize.org/discussion/comment/5493/#Comment_5493. This outlines three options, each with relative merits: international power networks, energy storage and mobile energy ships.)
With regard to the specific questions about energy transfer distance, and distances that should be avoided...
There might be potential benefits (e.g. capital cost, and energy loss efficiencies) in keeping inter-nodal power cable distances relatively short; but perhaps multiple solutions might arise, determined by local needs. For example, neighbouring nations need only install a cross-border power connection; whereas remote (small) islands face a challenge that could require a different solution. See the above comment link to see how different solutions could be adopted by different nations; and the role of a robust global power network [like the Internet, which is itself a network of smaller networks].
In the absence of a breakthrough in low cost, ambient temperature, superconductors long distance oceanic power cables (e.g. trans-Atlantic or trans-Pacific) are unlikely to be feasible.
Personally, I'd get most excited about a distributed grid that had a kind of market-function, kind of like what is described in this video (the good part starts at 15:13
@bernardsaw - We would love to learn more about producing hydrogen using solar energy - If you have any more details on it (any papers / reports published), please share it with us. Thanks.
Distance is not really a constraint for delivering chemical energy.
Most of major the power demand in many countries so far has been met by fossil fuels. The fossil fuels (solid, liquid or gas) have been used to generate power in concentrated form at convenient sites considering availability of the fuel and end use requirements. Fossil fuels in the form of coal, natural gas, LPG or crude or refined oils are easy to transport locally within a country and from country to country. For fixed (residential and commercial buildings and industrial sector) power is transmitted over both short and long distances from points of generation with inherent efficiency losses. For mobile power generation (trains, trucks, planes, cars), liquid or gaseous fuels are conveniently is use because of the ease of storage and transportation.
For renewable energy to replacement fossil fuels, similar end-use energy sectors and scenarios need to be considered with the added challenges of renewable energy intermittency and associated storage and transportation issues. The domestic and residential sectors are easy to cater for and local demands can be met with simple energy storage solutions. However, the industrial and transport sectors are much larger in size. Also, there are countries / regions around the globe which cannot meet all their power demands with locally available renewable energy sources or availability of infrastructure. Thus renewable energy has to be transported over long distances from one region or country to another (over many thousands of km). How it is to be done is a major challenge. Also the footprint of renewable energy generation plants, especially solar power plans is significantly larger than fossil fuel based power plants.
There are regions in the world which are rich in solar or wind energy much like the availability of fossil fuels in selected regions or countries. For example, a small area in the North West Australia can generate enough renewable energy to feed rest of the World due to availability of land and very high intensity of solar radiation fall. However, the issue is transportation / transmission of energy/power to countries where there is lack of sufficient renewable energy to meet local demand.
Sukhvinder Badwal
Storage Batteries
Battery technology is ideal for local storage and utilisation of renewable energy where long distance energy transportation is not an issue. Examples are residential dwellings/communities and commercial buildings and transport vehicles (cars, trucks, etc.). Typically energy use per day in a house hold varies from 2kWh to 20kWh and in poor countries it may be less than 1kWh. An electric car would require 25-100kWh storage depending on the distance to travel on a single charge (e.g. 100km to 400km). Thus battery storage an easily cater for this. Similarly battery storage in the MWh range can cater for local communities, commercial dwellings, etc.
One of the major advantage of battery technology is the efficiency losses for energy in and out are relatively small (typically less than 15%) thus increasing the overall efficiency to over 85%. Battery technology is reasonably advanced although increase in energy storage density, cycle life and overall life time would be beneficial in the long run. The major drawback is that for every kWh of energy storage, any additional kWh storage would require doubling the size of the battery and consequent weight.
Transmission of renewable electricity over up to few hundred km utilising existing infrastructure is another good option especially if it is complimented by battery storage to overcome intermittency of renewable energy technology either at generation or end use sites.
Battery technology, nevertheless has limitations for the transportation of renewable energy from generation (which may often be remote) to further away utilisation sites, especially over long distances with non-existent transmission infrastructure and overseas locations (up to several thousand km) where renewable energy availability is scarce.
Hydrogen
Hydrogen offers a very good alternative to renewable energy storage, utilisation and transportation to almost every corner of the world. Hydrogen can be easily coupled to renewable energy technologies and its utilisation generates no greenhouse gases or pollutants. There is no limit to distance over which hydrogen can be transported. However, there are substantial challenges for its generation, storage and transportation including increased cost and efficiency losses at each step. The energy content of hydrogen per unit weight is very high but extremely low per unit volume unless it is compressed at very high pressures, e.g. to around 700bar or converted to liquid form (-253oC).
Over 60 million tons of hydrogen is consumed per annum globally and is mostly produced from natural gas. It is worth mentioning that this entire current hydrogen production capacity accounts for less than 3% of the total global energy demand. Thus a significant increase in the hydrogen production capacity would be required (and that too from renewable energy sources) to make an impact as a clean alternative to fossil fuels.
So far the major use of hydrogen has been for ammonia production, and in oil refineries and methanol production with very small use (less than 2%) as an energy carrier.
A large percentage of ammonia, produced globally, is currently used in fertiliser production (about 80%) with other uses including explosives, pharmaceuticals, refrigeration, cleaning products and some industrial processes. It has also been used in small quantities as a fuel for transport vehicles and for space heating. Ammonia is an excellent energy storage media with 17.5wt% hydrogen content and it stays in liquid form above about 9-10 bar pressure at ambient temperature. The infrastructure for its transportation and distribution is already in place in many countries and between countries. However, if ammonia is to be used as a renewable energy transportation media, technologies for its efficient production, its reutilisation as a fuel (direct combustion or in fuel cells) or reconversion to hydrogen need to be developed with minimal overall life cycle energy losses.
Clean hydrogen generation using water electrolysis with coupling to renewable energy is well established now, however, the issue is cost and economy especially when the cost of entire infrastructure is considered (includes cost of renewable energy input technologies such as solar panels or wind turbines, electrolyser, clean water supply system, maintenance costs and lifetime of each technology). About 45-60kWh electric input is required to generate 1kg of hydrogen. Thus the cost of renewable energy has to be very low per kWh. At best 80-90% efficiency can be achieved for hydrogen generation via electrolysis. Electrolysers varying in size from a few kW to 100s of MW depending upon the application requirement can be installed.
The next major step is getting hydrogen fuel for effective utilisation and transportation over distances and to countries and utilisation sites with low renewable energy footprint. This is a major challenge. For residential and small scale stationary power generation, it is not such a major issue as space is less of an issue and hydrogen can be stored at low pressures (10-30bar). For hydrogen utilisation in transport vehicles, many hydrogen / fuel cell vehicle manufacturers have opted for high pressure (350 to 700bar) storage in light weight storage tanks but efficiency losses for compression are significant in addition to cost of hydrogen compressors. The alternative of solid state hydrogen storage technologies where over 6-8 wt% storage is required including hydrogen insertion and extraction have not materialised so far.
For long distance and overseas transport, hydrogen transport in compressed form is not feasible. Thus its transport in liquid form (-253oC) or converting it to a chemical form such as ammonia and others chemicals is being explored. However, there are major challenges in terms of cost and also efficiency losses.
Hydrogen or its chemical form can be combusted to generate energy at utilisation sites or converted to electricity and heat in fuel cells. Again the typical electric efficiency of hydrogen utilisation in a fuel cell is 40-50% with 30-40% available as a heat component if required. Apart from the current high cost of fuel cells and some lifetime issues, the lack of cost effective hydrogen storage technologies and distribution infrastructure is hampering the mass penetration of hydrogen as an alternative transport fuel.
For each area discussed above there are a number of sub-set technologies which all have a number of challenges.
The model I am most fond of is one where renewable energy is captured where it is most efficient to be captured and then that energy flows to where it is needed... which is everywhere. My model has solar farms built in deserts where the solar flux is the greatest. That energy flows electrically to the nearest coast. At the coast you now have everything needed to make renewable chemical fuels; electrical energy, H2O and CO2. Either hydrogen or ammonia or carbon fuels can be created. Once created, these fuels are loaded onto ships or pipelines and distributed as needed.
Right now, each fuel has its own set of challenges. Hydrogen has storage and transport issues. I don't know much about ammonia. I prefer renewable hydrocarbons, but high volume synthesis is a limitation. Once synthesized, the rest of the world is ready to utilize those hydrocarbons. Hydrogen and Ammonia require new infrastructure everywhere.
And just to be clear, Solar and Wind energy should always be used locally, as electricity, as much as possible.
As to overcoming the barriers, I am focused on renewable hydrocarbons. Substantial investments need to be made in technology that creates machines which create hydrocarbons. I have thoughts on that which I will share later.
In summary, the benchmark distance for transportation does not really exist on its own but is rather a function of many factors such as cost and feasibility of generation, transportation (transmission, distribution), losses, ancillary services, overhead, maintenance, demand patterns etc