Is this the future of solar?

[GotSmart]

Lately I have developed a passion for solar as an alternative to grid power.

Any idea of what the future holds would be a welcome read.  

http://fortune.com/2015/05/18/solar-power-ripasso/?xid=yahoo_fortune

 

 

[mariasman]

If you like solar, then you'll love Terrajoule's system (terrajoulecorp.com). I encourage you to spend some time considering it because the configuration is unconventional. It cannot be appreciated until it's understood properly.

I'll provide a synopsis. The main benefit of this system over other solar systems is low cost energy storage. This system provides 24/7 electricity without batteries, and the cost of their storage system is 1/5 that of chemical battery systems. The storage system is a conventional insulated steel pressure vessel normally used to contain propane.

It work like this: conventional solar concentrators heat a thermal oil. The hot oil is then used to generate superheated steam at about 600F. The pressurized steam is directed to the steam engine (i.e. the piston expander). This is were people get thrown for a loop. Why a piston steam engine? Well, the efficiency of this particular engine design is very high, and it does not vary significantly over its power range. It shows high efficiency at low outputs and at rated output. So, the engine modulates its output to meet load demands while showing good efficiency (like a Diesel generator). By contrast, steam turbines show good efficiency only at a narrow power range. Also, a good piston steam engine design is more efficient than a steam turbine at lower power ratings where this technology targets. Really, steam turbines are suitable only as large base load power units in central power plants. For decentralized energy the piston expander is superior (again, suitable for lower power ratings and highly variable power demands).

How does it work? The expander uses multiple pistons in a compounded configuration. During the day when hot oil is being generated, then the high pressure steam is directed to the first and smaller high pressure cylinder. The steam from that cylinder then exhausts and expands into several successively larger cylinders and may even get reheated using the hot oil to boost cycle efficiency. When additional energy storage is desired (basically, whenever the engine output can exceed load demands and there is room in the storage tanks), then the steam is exhausted while still under some pressure into the insulated steel pressure vessel that is filled with water. This heats and pressurizes the water in the tank. At night, steam is taken from the tank to drive the lower pressure cylinders of the expander (the higher pressure cylinders are not used).

BTW, I did some study on the basic engine design a while back that was last manufactured back in the 1930's. The engine design earned a reputation for high efficiency and extreme reliability. In this solar configuration the overall efficiency in converting incident solar radiation to AC electricity is in the high teens - better than conventional photovoltaics. System is fully automated, design life of more than 25 years - including energy storage, and negligible water usage (water is contained and reused). Very impressive for pre WW2 technology.

 

[GotSmart]

Mariasman;

What is the basic cost of a whole house system?

It would not work in a van for obvious reasons.  

 

[mariasman]

Of course it's not suitable for micro scale. In that setting you can't beat photovoltaic panels. I was sharing only because you expressed interest in the Ripasso solar thermal systems (also not micro scale).

 

[GotSmart]

Good information, but not for the basic user. This is a community size system.

Thanks for the input. I will be reading their site to see if any ideas click.

 

[mariasman]

Good information, but not for the basic user.  This is a community size system.

Thanks for the input.  I will be reading their site to see if any ideas click.

Of course, the system you linked in the OP is also a community sized system. I figured that was your interest, hence my introducing the Terrajoule system. It's a system that I believe deserves more attention, but is discounted largely because it's not understood.

 

[LeeRevell]

Terrajoule's system sounds like they are incorporating a Sterling Cycle engine design. I'd be interested in this for my property, if the cost were economically viable.

 

[mariasman]

Terrajoule's system sounds like they are incorporating a Sterling Cycle engine design.  I'd be interested in this for my property, if the cost were economically viable.

Oh no, it's a piston steam engine based on the proven Universal Uniflow marine steam engine (a compounded uniflow piston steam engine system) - with some modern twists that enhance efficiency. Right now the company is looking to displace Diesel engines otherwise used to power irrigation pumps. In a region with the right solar resource, then it's ideal in that application since the cool irrigation water is perfect as a heat sink for the condenser - it really boosts efficiency by getting a high vacuum on the condenser. The best features of the system in my opinion is the low cost and simple energy storage system that allows 24/7 operation, and the absence of exotic materials and designs (unlike modern Stirling engines). The only unusual component is the steam expander itself, but it's based on a proven design with a history of reliability.

Here's a simple video introducing the technology. Note that I have no association with the company. I just happen to be a position to understand the potential of the technology better than most based on my training. In my opinion (and of course I have my own biases), the system has potential in many applications - however, I don't expect it to get much attention any time soon (if ever) because it's not properly understood. It's not "the solution", it's just particularly elegant in many ways. A lot of development work remains to be done.

 

[jimindenver]

I see two possible futures for solar. Small solar and big solar.

On a small scale I can see the way I use my trailer. Panel to cover most loads direct with a moderate battery to handle surges and off times like over night. A transfer switch could sense if the battery was low and bring the grid on line so you would be off grid with a safety net. Add in passive solar and you could really make the utility cry.

Big solar/wind is proving feasible but the utilities have played it smart. They didn't need to develop the tech just like they didn't have to spend the money to see if rooftop installations would work.  The utility here hates those except if they own them, renting the roof for a pittance. The same will be true for big solar. Once the tech is viable the utilities will build their own, pass the cost on to us and collect the free power forever.

 

[LeeRevell]

Here's the wiki on the Uniflow Steam Engine. It mentions that a two-stroke motor can be converted to a Uniflow Steam Engine, but they also list some serious drawbacks to the system, which has been around since 1827. It has been used in locomotives and in large ships and ferrys.

http://en.wikipedia.org/wiki/Uniflow_steam_engine

The main drawback in trying to use it for vandwelling would be the steam generation and holding tank. The necessary mirror and water piping on the roof would be very clumsy and bulky. In a fixed land setting it could work. But any system using live steam under pressure has inherent dangers.