Banking sun and wind energy

Banking sun and wind energy
Sami Tuomi and Tanja Kallio with some solar panels. Use of solar energy is increasing rapidly also on the Otaniemi campus. The 920 rooftop solar panels of the TUAS building and the Computer Science building generate enough electricity to satisfy some 6% of the annual requirement of these buildings, and up to 20% in summertime. Credit: Jaakko Kahilaniemi

The EU has a hard goal: it wants the Member States to cut greenhouse gas emissions to a fifth, or even a tenth, of the present level by 2050.

Professor Tanja Kallio and doctoral candidate Sami Tuomi consider the realisation of this goal entirely possible.

"In Denmark, for example, already accounts for 40% of and the target is to raise this share to 60% in a little over a decade. In theory, there is no reason why all couldn't come from ."

A problem that needs solving before that concerns storage.

Three grams versus two tonnes

The Sun radiates 4.3 × 1020 joules of energy per hour on the Earth – about as much as the human race consumes in an entire year. Sunshine and wind can, however, be absent when there is a need for energy, and large-scale storage involves many challenges. One of these is platinum, the precious metal familiar from luxury jewellery that sells for about €30 per gram. In the storing of renewable energy, platinum acts as an electrocatalyst that enables solar- or wind-generated electrical energy to be stored as chemical energy and, in turn, the conversion of this chemical energy back to electricity.

"Catalysts account for about a fifth of the process' costs. The EU has listed platinum and many other catalysts currently in use as raw materials of critical importance. This means that they threaten to either run out globally and, prior to this, become astronomically expensive or that they are sourced from geopolitically challenging countries, where their production is not secure," Tanja Kallio explains.

Kallio and her group aim to replace platinum by developing catalysts out of cheaper and easier to find raw materials, such as iron. The price difference is enormous: a hundred euro buys about three grams of platinum, but more than two tonnes of iron. Unlike platinum, however, iron is not a good because its surface is susceptible to passivation in air.

One of the materials tailor-made by the group is a carbon nanotube with excellent electrical conductivity. Embedded in its surface is an iron particle, which is protected by a graphene layer and serves as a catalyst. It is, thanks to its manufacturing method, very active, which means that only a little electrical energy is wasted in the storage process. This makes the process economically viable.

"We've also produced nitrogen-doped carbon nanotubes. The tube itself is poor to react, but when you remove a carbon atom from the surface and replace it with nitrogen, you create discontinuity points, which are catalytically active," says Sami Tuomi.

Nitrogen doping, i.e. precipitation, is a straightforward process. First, the carbon nanotube and a solvent are combined in one vessel, while a nitrogen-containing compound and a solvent go into another. After this you stir, then merge the mixtures, and then stir again. Finally, the desired material is removed to undergo heat-treatment. Kallio says this simplicity was a conscious choice.

"We wanted a process that would be as easy as possible to scale up and commercialise."

Will it last?

When renewable energy is stored in large amounts and for a long time, it is usually done using hydrogen. The electricity generated by a solar panel or a wind turbine is transmitted to an electrolyser unit, which consists of two end plates that are surfaced with a catalytic material. In addition to electricity, one end plate is fed with water, which decomposes into oxygen and hydrogen molecules on the surface of the catalyst. The oxygen leaves the second end plate in pure gaseous form and the hydrogen is collected into storage tanks, enabling its further use or later conversion back into electricity. Storage tank volumes can range from the size of a shipping container to giant subterranean spheres the size of a small apartment building.

"Smaller containers might be suitable for storing, for example, fuel for hydrogen vehicles," Tanja Kallio reckons.

"This would also be sensible, as studies have indicated that the most economical system would be one in which hydrogen is consumed in pace with production output. In other words, renewable peak energy would yield hydrogen, which would in turn be consumed by hydrogen cars."

Tailored catalysts have some way to go before they are ready for industrial application, however. Kallio acknowledges that, even though their group has discovered several promising and interesting catalysts, it remains a mystery how and why some of them work. Another major challenge is to demonstrate that catalysts, which have been found to work excellently on a small, laboratory scale, can also serve well on a larger scale and over a sufficiently long time.

"Timescale is one of the biggest challenges. A catalyst should function for at least five years in a commercial application, but implementing a demo of such length isn't very realistic," Tuomi says.

"I myself think that we'll start with shorter times and see if any degradation occurs. This will allow us to examine how well the catalyst holds up or, if it doesn't hold up, what is the reason behind it. The commercial challenge will thus be resolved alongside the scientific problem," Kallio believes.

Three culprits out of four

A positive solution could have an enormous impact on , which would help combat climate change. An example from the other side of the Atlantic illuminates this huge potential.

"In the United States, electricity generation causes 29% of greenhouse gas emissions, and coal plants create 75% of these. If coal power were replaced by wind- or solar-powered electricity, the country's greenhouse gas emissions would fall 22%," says Sami Tuomi.

Such a reduction sounds utopian during the term of Paris climate accord shelver Donald Trump, but thankfully there is hope elsewhere. Asian giants India and China, for example, have already decided to reduce the number of coal plants because it is clearly cheaper to generate electricity using renewable sources. Kallio and Tuomi underline that applications can be found in other sectors as well. The activities that cause greenhouse gas emissions can be divided into four roughly equal categories: electricity generation, industry, transport and other activities like agriculture.

"We can influence the first three of these. Industry, for example, consumes enormous quantities of hydrogen, which is currently produced from natural gas. Our system would enable its manufacture from water with renewable energy."

Just one hydrogen-powered fuel cell car has been registered in Finland, and these water vapour-exhausting vehicles are still rare elsewhere in the world, too. But change is afoot: auto industry behemoth Toyota in particular is investing strongly in fuel cells and Tokyo intends to spend €350 million on the city's hydrogen infrastructure prior to the 2030 Olympic Games.

"Electric cars have proliferated rapidly because infrastructure is being built for them. If hydrogen-powered renewable solutions become more common, also the infrastructure would be built," Kallio says.

Hydrogen cars would be a good match with Finnish driving culture.

"Electric cars are great for urban traffic, but it is unlikely that you'll be driving long distances to the summer cottage or touring Lapland in one anytime soon."


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Promising results obtained with a new electrocatalyst that reduces the need for platinum

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Oct 09, 2017
"In Denmark, for example, renewable energy already accounts for 40% of electricity generation


Correct statistics, but false information, since the wind power output is exchanged with Norway and Germany in a virtual battery scheme to level out the load. The percentage should therefore be counted in all of their systems - unless you want to pretend that coal power bought from Germany is renewable.

Denmark is a non-example because it's a small country nestled between two huge electricity markets - the nordic grid and the continental synchronous grid - which means it matters very little what they do: the variations and disturbances sink into the larger grids and they can post impressive figures that simply aren't attainable elsewhere in the larger scale.

In scale, Denmark is like a single county in the US. You can pack one full of wind turbines and simply sell the power out, and then claim you're green because on paper the numbers match.

Oct 09, 2017
well, not quite as small as a county, though there are counties with similiar populations (number of electricity users)

the most economical system would be one in which hydrogen is consumed in pace with production output. In other words, renewable peak energy would yield hydrogen, which would in turn be consumed by hydrogen cars."


The sticking point is in the distribution. Gas can already be distributed throughout the continental european gas grids, which have enough capacity just in the pipes to hold several hundred TWh worth of energy (compare, all the fjords in Norway could hold ~85 TWh of pumped hydro).

Problem is, the gas grid doesn't tolerate hydrogen because it's very explosive, doesn't liquefy easily for storage, and leaks. Up to 30% can be added though.

Oct 09, 2017
"Electric cars have proliferated rapidly because infrastructure is being built for them. If hydrogen-powered renewable energy solutions become more common, also the infrastructure would be built," Kallio says.

I think there's a bit of a difference in difficulty, here. Building a power outlet (even one that delivers a substantial wattage) is far easier and cheaper than building a hydrogen recharging station.

Maybe for the niche markets that need fast refueling and long distance (long haul freight) it would make sense to develop this with charge points near highways. For the personal mobility market EVs are superior (also from a POV of efficiencey).

IMO hydrogen makes most sense in terms of large storage units for grid stability and backup.

Oct 09, 2017
Building a power outlet (even one that delivers a substantial wattage) is far easier and cheaper than building a hydrogen recharging station


Delivering that wattage is a question by itself though:

https://evobsessi...v-fleet/
Norwegian Grid Struggling To Keep Up With Growing EV Fleet

In an article on the Norwegian site Teknisk Ukeblad the problem of the grid trying to keep up with demand is discussed. Bjørn Brattelid working with the grid operator Lyse Elnett puts it this way:

In recent years, the network demand has grown drastically. (...). Today we balance on a knifes edge in several locations. When people install 22 kW chargers to charge their Tesla in outlying areas, it can be a heavy burden on our local network. In case of large voltage variations, it can even result in light flashing in peoples homes.


Norway has just about 125,000 electric cars. Charging one up from a regular socket can literally take days

Oct 09, 2017
The most sensible option is to use whatever hydrogen you can and need directly, as it is a chemical precursor to many products such as fertilizers, and further catalyze the majority of it into methane and heavier (liquid) hydrocarbons for storage and transport.

That way the already existing fleet of vehicles can readily accept the energy stream and more expensive electric or fuel cell cars become unnecessary until their prices drop to a competitive level.

Oct 09, 2017
"Electric cars have proliferated rapidly because infrastructure is being built for them.


Rather, it's for the subsidies paid for them.

https://www.maste...v-costs/

"What happened in Denmark was similar to the experience in Georgia, where the state's legislature voted to end its nation-high EV incentive program of $5,000 per vehicle, and to add a tax to EVs to account for road wear and tear. After the incentive was eliminated effective July 1, 2015, car dealers couldn't give EVs away."

"It appears from all the EV data we have examined worldwide that no country has crossed that gap from early movers/EV advocates to mass market appeal. It is all about battery costs, range anxiety, and subsidies. Until there are significant technological breakthroughs, government subsidies cannot be abandoned."


80% drop in sales after subsidies were abandoned.

Oct 09, 2017
I invite electrolysis researchers out there to help to develop my concept for "Deep Sea Hydrogen Storage" as described in my blog post "Off-Shore Electricity from Wind, Solar and Hydrogen Power"
https://scottishs...n-power/

"The diagram shows how hydrogen gas can be used to store energy from renewable-energy platforms floating at sea by sending any surplus wind and solar electrical power down a sub-sea cable to power underwater high-pressure electrolysis to make compressed hydrogen to store in underwater inflatable gas-bags.

It's potentially very cheap because no super-strong pressure containment vessels are required - the ambient hydrostatic pressure which is proportional to depth serves to compress the hydrogen gas to containable densities."

Oct 09, 2017
"Charging one up from a regular socket can literally take days" WRONG!!

A European type F plug has a current capacity of 16 amps and is fed from a 220 - 240 V source. So, the nominal charging rate is over 3.5 kW, which after 12 hours would transfer over 42 kWh of energy to an EV battery, enough for over 160 miles of additional range to your Tesla.

Now, if you were silly enough to try to charge your EV from a European type C (2.5A) shaver outlet in your hotel room, it would take days, particularly if you accounted for the power loss in the fine gauge shaver cord running from your hotel room to the hotel garage. :)

Oct 09, 2017
ScottishScientist: You have to solve the issue of chlorine generation from the salt in the sea water. It fouls up the system.

And the storage of gaseous hydrogen needs to be at 40 - 80 MPa to have any meaningful energy density for vehicle use - that would be 4-8 km deep. You may also want to check your calculations about the lift produced by a 50 cubic meter balloon of hydrogen, however compressed, under kilometers of water: it's not very easy to anchor down and it's liable to burst from the sheer force of it.

But nevermind the hydrogen, just the flow of the pressurized gas from the depths would be enough to run a turbine.

Oct 09, 2017
A European type F plug has a current capacity of 16 amps and is fed from a 220 - 240 V source. So, the nominal charging rate is over 3.5 kW, which after 12 hours would transfer over 42 kWh of energy to an EV battery, enough for over 160 miles of additional range to your Tesla.


Meanwhile in the real world, outdoors sockets for car heaters in parking lots are typically rated at 10 Amps, and are on a 15 minute on/off alternating rotation so the owner of the parking lot doesn't have to pay extraordinary fees for the grid connection - they're sized for 2000 W interior heater + 400 W block heater. The practical power delivery is therefore about 1.2 kW over time, minus efficiency losses.

Charging a 100 kWh Tesla battery from empty at 1 kW takes four days.

Oct 09, 2017
It's one thing to have suitable sockets and all, but from the power delivery standpoint, if everyone were to install their own superchargers, the utility company has to upgrade your service panel, the distribution transformer, and the power lines to match because the grid has to be able to safely deliver what everyone's capable of drawing out of it - potentially at the same time. You can't just arbitrarily pull wires and slap new sockets everywhere.

And you have to pay for that.

Oct 09, 2017
The charging of EVs is just evolving but overnight charging is a natural first choice for the an EV owner living in a single or duplex family dwelling with a garage or private laneway since the circuitry from the power panel and is pretty standard in North America for charging rates up to 9.2 kW (over 101 kWh of charge in 11 hours) without taxing the grid during these off-peak hours.

Standard circuitry in USA and Canada is:
- Typical outlets are 15A, 115 V (1.2 kW) using 14 ga. wiring,
- Kitchen counter outlets are 20A, 115V (3.45 kW) using 12 ga. wiring,
- Dishwasher outlets are 30A, 230V (6.9 kW) using 10 ga. wiring and
- Electric stove outlets are 40, 230V (9.2 kW) using 8 ga. wiring

For condominium dwellers, overnight charging parking spots will be introduced gradually as more of the owners switch to EVs.

Eventually on-street wireless parking options should become available as an overnight charging option.

Oct 09, 2017
You can't just arbitrarily pull wires and slap new sockets everywhere.

And you have to pay for that.
That's right - you have to pay for the electricity you use. We had a Nissan Leaf for over a year. Charged it off a 110 volt outlet. Used the second car that used gas - if we needed to go on long journeys. So an 80 mile range car - satisfied about 95% of my wife's driving needs - without even going up to 220 volt charging - that would not need any wiring upgrades. Current gen EV's are over 200 mile range - and will work fine on 220 volt charging. The thing people miss is that the transition is going to take time - and yes - grid upgrades will have to happen. They have to happen every time someone builds a new home. But customers are paying for the power - so the utility does not mind providing the upgrade - as that is what utilities do.

Oct 10, 2017
https://scottishs...n-power/

ScottishScientist: You have to solve the issue of chlorine generation from the salt in the sea water. It fouls up the system.

Already noted

"Be aware that for undersea electrolysis in order to produce oxygen as the anode gas, a custom electrolyte solution will have to be used. If you try electrolysing sea water directly you get chlorine gas off at the anode, which is not so easy to dispose of and can be poisonous.

So the technique will be to separate the custom more-concentrated electrolyte solution from the sea water by a semi-permeable membrane and allow pure water to pass through it by osmosis from the relatively dilute sea water."

Problem - membrane fouling / piercing by sea-life.

Alternatively pump down rain or shipped-in water from the surface to dilute electrolyte solution.

Oct 10, 2017
And the storage of gaseous hydrogen needs to be at 40 - 80 MPa to have any meaningful energy density for vehicle use - that would be 4-8 km deep.

At only 2 km deep the density of hydrogen is 16 g/L so a 50 m^3 (50,000 L) gas bag will store 800 Kg of hydrogen.
You may also want to check your calculations about the lift produced by a 50 cubic meter balloon of hydrogen, however compressed, under kilometers of water: it's not very easy to anchor down and it's liable to burst from the sheer force of it.

The buoyancy lift doesn't increase much with depth because the displaced volume of water's density doesn't increase much (+0.3% max) with depth.
Archimedes Principle - https://en.wikipe...rinciple
So if the bag doesn't burst near the surface then it shouldn't burst at 2 km depth either.
Lifting bag https://en.wikipe...ting_bag

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