Renewable Reality: Feasible and Inexpensive

‘Aiming for 90% or more renewable energy in 2030 in order to achieve climate change targets of 80-90% reduction of CO2 from the power sector leads to economic savings, not costs.’

WHO: Cory Budischak, Department of Electrical and Computer Engineering, University of Delaware, Newark, Department of Energy Management, Delaware Technical Community College, Newark, USA
DeAnna Sewell, Heather Thomson, Dana E. Veron, Center for Carbon-Free Power Integration, School of Marine Science and Policy, College of Earth Ocean and Environment, University of Delaware, Newark, USA
Leon Mach, Energy and Environmental Policy Program, College of Engineering, University of Delaware, Newark, USA
Willett Kempton, Department of Electrical and Computer Engineering, University of Delaware, Newark, Center for Carbon-Free Power Integration, School of Marine Science and Policy, College of Earth Ocean and Environment, University of Delaware, Newark USA, Center for Electric Technology, DTU Elektro, Danmarks Tekniske Universitet, Lungby, Denmark

WHAT: Working out how you could power a region with renewable electricity and the cost of doing it

WHEN: 11 October 2012

WHERE: Journal of Power Sources, 225, 2013

TITLE: Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time

This research from the US is quite practical. The researchers looked at the electricity use from 1999 – 2002 in the ‘PJM Interconnection’ which is a power grid in the North Eastern USA that includes Delaware, New Jersey, Pennsylvania, Virginia, West Virginia, Ohio and parts of Indiana, Illinois and Michigan.

They wanted to know what a renewable power grid would look like, how much it would cost and how you could do it. Research excitement!

The PJM Interconnection power grid area in the blue lines. Pink stars are the meteorological data sites (from paper)

The PJM Interconnection power grid area in the blue lines.
Pink stars are the meteorological data sites (from paper)

So what does a renewable power grid look like in this area? It involves a combination of renewables, which are onshore wind, offshore wind and solar in multiple locations which provides the greatest range of renewable power sources (if the wind is still in one state, it may be blowing in the next state).

The first hurdle this team had to jump was storage. The most popular storage model for renewables is wind-hydro hybrids (which I’ve written about previously here), however in this corner of the USA, there’s not much hydro power. So the paper looked at the options of electric vehicle grid storage, hydrogen storage and battery storage (lithium titanate batteries for those playing at home).

They used the data from 1999-2002 to model the hourly fluctuations of electricity demand, which averaged out at 31.5 Gigawatts (GW) of 72GW of generation. They then matched the load hour by hour with renewables and worked out which was cheapest.

They calculated the costs with a level playing field, which means no subsidies. No subsidies for renewables, but also a magical time when there’s not billions upon billions of dollars each year for fossil fuel subsides as well.

The results were that a renewable grid with 30% of coverage produced 50% of the power required for the sample years, while a renewable grid that provided 90% of the power coverage produced double the power required and a renewable grid that provided 99.9% of the power coverage produced three times the energy required. The researchers found that an overproduction of renewable electricity was preferable to trying to exactly match the power required and also reduced the need for storage.

A few of the benefits they found were that offshore wind and solar often generate when inland wind doesn’t, and that there was greater over-supply of power in the winter months which could allow for natural gas heating to be replaced by renewable electric heating.

Renewable power in the 99.9% model only needed fossil fuel back up 5 times in 4 years (from paper)

Renewable power in the 99.9% model only needed fossil fuel back up 5 times in 4 years (from paper)

What about the costs? The researchers looked at what the cost was for power in 2010 dollars and then adjusted for efficiencies to estimate the 2030 cost of power for the model and the infrastructure.

The 2010 cost of power was 17c per Kilowatt hour (kWh), while a renewable grid with 30% coverage would cost 10-11c per kWh, a 90% renewable grid would cost 6c per kWh and a 99.9% renewable grid is at parity with the fossil fuel grid at 17c per kWh.

The reason the 99.9% cost is higher than 90% is because filling the gap of that final 9.9% requires more infrastructure to further diversify the grid, but I think the most important thing they found in their research is this:

‘The second policy observation is that aiming for 90% or more renewable energy in 2030, in order to achieve climate change targets of 80%-90% reduction of CO2 from the power sector, leads to economic savings, not costs.’

Yes, even in coal country in the USA, switching to a hybrid renewable system (in a level playing field) is cheaper than the current cost of fossil fuel electricity. It also comes with the added benefits of no mercury poisoning from coal fired power plants too!

The paper concludes that while excess power generation in a renewable grid is a new idea, it shouldn’t be too problematic since it saves on storage needs and is the most cost-effective variation.

Their advice for plucky leaders who would like to make this grid a reality? The most cost-effective way to build this grid is to aim for 30% renewables now, and phase in the rest to 90% in 2030. Each step along the way to more renewable power will not only be a climate saving step, it will save money as well.

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How Does Your Wind Farm Grow?

Calculating what the global saturation point for wind energy would be and if we can generate enough wind power to power half the globe.

WHO: Mark Z. Jacobson (Department of Civil and Environmental Engineering, Stanford University, Stanford, CA)
Cristina L. Archer (College of Earth, Ocean, and Environment, University of Delaware, Newark, DE)

WHAT: Predicting the effectiveness of scaling up wind power to provide half the world’s power requirements by 2030.

WHEN:  September 25 2012 PNAS, Vol 109, No. 39

WHERE: Proceedings of the National Academy of Sciences of the United States of America

TITLE: Saturation wind power potential and its implications for wind energy

I learnt about a new law today; Betz’s Law. Betz was a guy who decided to calculate exactly how much energy could be extracted from the wind by a turbine at any given time mathematically (as you do). He worked out that no turbine can take any more than 59.3% of the energy from the wind. To be able to conceptualise this, you have to think about wind like a physicist. The first law of thermodynamics states that you can’t create or destroy energy; you can only convert it to different forms. Therefore, all wind is just energy in a certain form, and in any system there is a point where the transformation is most efficient and beyond there it takes a lot of effort to get any more energy from the system.

There’s a really cool project being done in the US, where a website has taken data from the National Digital Forecast Database and created a visual representation of what wind would look like if you could see it move. It’s strikingly beautiful, and looks a lot like a Van Gogh painting.

Wind Map by Fernanda Viegas and Martin Wattenberg of hint.fm

The question this paper looks at is: since there is a limit to the amount of energy you can take from a turbine, what is the maximum wind power that can be extracted from a geographical area? They called it the ‘Saturation Wind Power Potential’.

They came up with some interesting findings, as well as probably having a lot of fun along the way because they used 3D Models to do it (I’m telling you, my chemistry molecular model kit was much more like playing with Lego than actual ‘science’). They got into the detail and calculated the potential wind power at 10m off the ground, 100m off the ground (the standard height of a wind turbine) and 10km off the ground in the jet stream.

They then looked at whether it would be possible to scale up wind power globally to meet 50% of the world’s power needs by 2030. Actually measuring the wind power potential for more than 1 Terrawatt (TW) of energy is not possible as there isn’t enough wind power installed yet. But they did mathematically work out that we would need 4million 5 Megawatt (MW) turbines to supply half of the world’s electricity needs in 2030 (5.75TW).

They did four simulations with different turbine densities, because how close together wind turbines are affects their ability to produce power. Put them too close together and they start stealing their neighbour’s wind power. Overall, up to 715TW, the increased number of turbines increases the amount of power in a linear straight line. Once you get above that it slows down and flattens out – once again you need to put much more effort in to get power out.

Predicted wind power saturation potential (from paper)
Grey line – global wind power potential, black line – wind power potential on land only

The saturation point, where no matter how many more turbines you add, they’ll just be stealing energy from each other and not adding anything to the total, was 2,870TW of power globally. Interestingly, they found the wind power available in the jet stream (10km above the ground) was 150% greater than the wind power available 100m above the ground.

There were also some big changes to the results depending on the density. If we placed 4million 5MW turbines and packed them in at 11.3 Watts per m2 (W/m2), they would be too close together and the collected power wouldn’t match the target for half the world’s power by 2030. If you spread them out to 5.6W/m2 the output is still too low. However, once you’ve got them spaced at 2.9W/m2, they produce enough power to meet the required demand.

4million turbines meet demand when they’re 2.9W/m2 apart or further (from paper)

So it turns out wind turbines don’t like it when you cramp their style. But, you can pack them in a bit tighter, only if you then have enough space between your wind farm and your neighbour’s wind farm. It’s a bit like playing wind farm Tetris.

What does this mean though? It means that we can ramp up world wind power production to levels that will meet half our power needs in 2030, which can be integrated with hydro, solar and other renewables with smart grids to power our cities and lifestyles without burning fossil fuels. But it also means we need to think about where we are putting wind farms and how much space they need to be as efficient as possible. We need that renewable energy, so we can’t cramp the wind turbines’ style!