Essays
As simple as possible, but no simpler.
Einfall is the German word for ‘insight’, ‘invasion’, or ‘bright idea’, which she discovered while reading the wonderful ‘How to Solve It”, by Polya.
Insights by Danielle Fong
notes from a girl from the future
Insights by Danielle Fong 
Hello danielle,
You are really special! I believe that God has given you special gifts that would be a blessing to many others. I look forward to your great contribution!
Jeremy
How large would an air storage unit need to be to store the energy produced by the average run of the mill wind farm. The world is full of ideas like this so the future seems very bright!
You probably want 6-8 hours of storage per turbine, which is 6 – 8 standard shipping containers work of air tanks. A fair amount but not too much, at half the cost of a turbine.
Danielle, I wouldn’t mind talking to you. There’s a designer in Vancouver who has some great ideas for compressed air. I’d also like to send you a design proposal. My email is waub@hotmail.com
Brennan.
how fast the energy storage system could response to support the grid? how fast the transient rensponse compared to electrochemical battery storage?
I am working on AC-module for solar system…your idea is a bright future.
Depends on the arrangement. We might put this behind a VFD for sub-cycle response time — otherwise we have the same timing characteristics as diesel gensets which can respond in < 4 seconds.
That’s wonderful…Battery storage is not good for our environment. It contains poisoneous materials. I am pretty curious and concern about the rensponse time and transient stability, How it works with VFD? Actually I have made one small VFD (Variable frequency drives), I implement Space Vector Modulation for generating pure sinusoidal waveform. But it is a small scale VFD (less than 1 KW).
How does lightsail energy’s compressed air energy storage compare to pumped hydroelectric energy storage. Cheaper, better? Neither?
More flexible, cheaper on a power basis, more geographically locatable, about as efficient, more dense, provides heating, cooling, recovers heat and converts to electricity.
Have you thought about how this could be deployed at existing coal-fired power plants to capture all the waste heat that remains unused?
Yes, it’s a good idea. But utilities aren’t fast moving…
wow. you’re really hawt.
Danielle,
Congratulations on a brilliant idea with the compressed air storage technology! Does it increase efficiency to change the nozzle type as it does with combustion engines? Also, could this technology be reduced in size to make it usable as a power source in cars?
Yes, and yes.
Hi Danielle….wondering about 2 things:
1)How hot is the water which is generated by the compression process?
2)If the water is stored, rather than used immediately for heat, how long does it retain its heat, with economically-practical levels of insulation?
Thanks
It depends — we aim for about a 30 C ∆T.
If you lose the whole ∆T, it is as if the atmosphere is your thermal battery. The efficiency scales down by T_atm/T_hot but it is not so bad — about 10% relative efficiency, or a 6-7% loss.
Also: Danielle, are you familiar with GE’s “ADELE” project? They also are attempting to capture and re-use the heat from compression—the main difference, from what I can tell, is that they’re routing air through some sort of ceramic material and storing the heat in the material, rather than using water. I believe their lead guy on this is Matthias Finkenrath in Germany.
It would be interesting to see a comparison of the pros & cons of the two methods.
Yes. As you can imagine the distinctions between using water instead of air, and storing heat at 600 C, are legion. It’s a completely different set of mechanical challenges.
I think ours are easier. PLus we can use waste heat. But this comparison is not obvious.
From the outside it looks like our velocity of development compares favorably with ADELE, but it is hard to tell.
I’m glad I asked Google who this Danielle Fong on LinkedIn is – this is a fabulous (both in significance and style) collection of insights that you’ve shared here.
The potential of the LightSail tech is enormous, both as marginal/balancing power and as a way to end the gratuitous waste of vast quantities of low grade heat, and your thoughts in June 08 regarding choice of work (futility of BigCo), the importance of being honest (pessimism to Californians?), and the admirable but ineffectual and distracting nature of hippies really resonated with me.
Utilities may be slow moving by SFBay standards, with screwed up priorities created by oversights in their privatisation/the regulatory framework which governs them, but they’re far from stupid and irrational. Doubly so when compared with consumers or governments – and they’re more solvent too… ;-)
Who “hurts most” in the industry?
In the UK it is private developers/generators chasing (absurd) government subsidises for renewables. They are installing generation equipment in the middle of nowhere and on the end of a fairy marginal grid connection. The grid companies (National Grid and Distribution Network Operators) have the ultimate say as to whether connection to the grid is permitted or not and how much it’ll cost to upgrade the infrastructure, so anything that you can do to mitigate those costs (or up-rate your generation for a given cost) is very much of interest. These folks are already installing “experimental” generation equipment so “experimental” time-shifting equipment isn’t too much of a leap for them.
Larger industrial customers are also in a position to manipulate pricing structures. I know that Milford Haven Refinery for example used to be (probably still is, but my father no longer works there) paid more to reduce their electrical demand during peak periods than it cost to run emergency Aggreko diesel generators – so whenever possible they took the cash and went off-grid. There would be no operational problem for them if they didin’t either – they would just make slightly less cash. Far less of a deal than a (regulated) utility that was required to rely upon the time shifting equipment to meet demand, with the regulation being the primary reason that the utility didn’t want the Aggrekos (or time shifting tech) sat on their balance sheets.
Is there a market for “buffered emergency generator sets” comprising packaged storage and generator? An asset that you require for operational purposes (backup generator) that you can now turn into an income stream rather than merely a cost?
Frequency stabilisation? Active harmonic cancellation? Driving a nicely packaged load/source via IGBTs to clean up the AC sine wave and reduce the transmission losses/upgrade grid capacity during peak periods?
I’ll add LightSail to the list to watch anyhow! Should you find yourself in presenting in England I’d love to be in the audience. The (tea) kettle is always on should you find yourself lost in Cambridge too. :-)
Yes, it is a very contorted market structure. Oh well.
Yes, there is a good market for what you suggest. There are a zillion markets, though, so the judgment comes in the form of picking the right one :-)
Hi Danielle,
Very impressive work! Have you worked out the equipment cost for each kWh energy capacity? Just wondering how this comparing with batteries. So each of your storage system will include a motor, a water tank, a pressurized air tank, nozzles, compressors and pipes. How well do you regulate your output electricity to match the grid? When you say you are 90% thermal dynamic efficient, do you mean you can consume 100kWh electricity at the begining and generate 90kWh electricity back into the grid? Thanks a lot!
Congratulate you on your curiosity; sorry for the short supply.
Mostly; it’s not proven till volume manufacture.
We beat all existing battery systems on capex by about 3 – 10x (except lead acid), and LCOE by 4x – 40x.
Theoretically sub-second variation is possible with some fancy power electronics. We’re giving ourselves several minutes for our first product though.
It means that purely thermodynamic losses only account for 10% electricity loss, whereas it would account for far more in traditional CAES systems. We are still working on reducing pumping losses, friction, etc.
Danielle,
Have you spoken with Brayton Energy LLC about their hybrid solar project for air compression? http://www.braytonenergy.net/
Not yet but I think it’s a good idea.
Danielle
You convert renewable energy to electricity then store it as compressed air then convert it back to electricity as needed.
Wondered what you thought about CSP (Concentrated Solar Power) power tower technology with molten salt heat storage. The energy is collected and stored as heat then converted to electricity as needed.
Yes we’ve thought about it and may apply to the ARPA-E FOCUS FOA on that topic.
Just curious if you have looked at direct mechanical linkage between wind turbines and air compressors and how the conversion loss tradeoffs compare?
It’s not a bad idea but it’s a lot of additional complication. It’s the sort of thing you might do in a third or fourth gen product.
How does lightsail energy’s compressed air energy storage compare to flywheel energy storage? It looks like the only advantage is transportability.
Hi Danielle,
In 2010 I developed the same system but further theoretical calculations I didn’t do (absence of financing and application in my country). I calculated system for the private house (about 30-60 kWh of energy and 10 kw the engine). The general estimated efficiency of system a charge – discharge at me turned out 60-80% (comparably to lead batteries but is cheaper on summary period of maintenance of 30-40 years). Its application I saw in energy storage from alternative power engineering (with a non-constant cycle of a charge) and the spare power supply in case of sudden energy disconnect (in exchange the diesel of generators and the UPS). I am glad for you that the technology works. I would like to share the ideas on construction of this system. Please write to me.
Hi, sorry to not get to this. Feel free to send me what you’ve got to my email, but please note that we’re very much on our own plan at this point.
Danielle, are you familiar with the new circuit breaker technology being developed by ABB, the European power and automation company, which should allow high voltage DC transmission lines to connect with local AC networks safely? (reported in MIT Technology Review, Energy – 2013, p 3) Could there be an opportunity for LightSail to function in both AC and DC networks for storage?
I’m not a scientist, so please excuse me if this is a stupid question!
Greg
When I watched your Solve for X video, a random thought I had was “I wonder how much of that water spray ends up evaporating…”.
That led me to wondering if enthalpy of vaporization could also be used as a buffer for the compression heat – say by adding something with a boiling point just above environmental temperature to the working fluid.
You’d trade the insulated water tank for some sort of condensate reclaimer (no idea which is cheaper), but could store the captured heat almost indefinitely.
So my question is, have you experimented with this? If so, what made you ultimately choose water for heat storage instead?
There’s relatively little evaporation because the temperature never goes up much and the volume is reduced so much. The saturation vapor density is a function of temperature almost exclusively, so by the time you’ve finished compressing, you usually net condense a huge amount of water.
If you’re doing an open cycle, water can’t be beat. Otherwise you have a problem with reclamation.
P.S.: I realize I’m grossly oversimplifying (especially when talking about a “boiling point” in the context of large pressure changes), but you get the idea I hope.
Hello Danielle!
My name is Jonathan Rogers I am pursuing my undergraduate as a Mechanical Engineering student at the University of Arkansas. I have currently been working on a sustainable idea using solar panels to help a transportation problem at the University.
In the progression of my work I spoke to Douglas Hutchings, who is currently managing his own startup PicaSolar (http://picasolar.com/) which uses his technology to increase solar cell conversion efficiency while reducing the number of silver gridlines. His work has demonstrated gains of 15%(relative) in the lab! I am very interested in your work for Lightsail and think he may be a helpful contact as you progress and maybe work with wind and solar energy!
As an undergraduate with aspiring entrepreneurial ideas, I’d be very interested in an internship with your company. Who would be the best person to send my resume?
Thanks!
Jonathan
You can send your resume to me, but unfortunately we’re not quite at a stage where we can support a real internship program — it’s is very very opportunistic.