Embedded Computers and Solar

The Raspberry Pi a small, inexpensive, full-featured computer  

Lately, I've been going down the rabbit hole of learning about embedded computers and it got me thinking about how these cool devices might benefit solar energy systems.  Embedded computers are essentially modern desktop computing power in a much smaller size (i.e. deck of cards) and priced in such a way that they could be almost be viewed as disposable (>$25).

My first thought was that embedded computers might control solar systems or aid with the reporting of data. Any decent residential inverter does this pretty well already with a variety of data input and outputs pre-loaded.  On the solar thermal side of things, energy metering packages could be built for well under $100 in parts which could reduce the cost of these types of add-ons for a small residential system so there could be a solid application there competing with products like the Apollo package.

A solar toaster?  Maybe not, but solar powered entertainment equipment is likely

Turning this computer-to-solar relationship on its head, solar PV might actually help make these little computers even more autonomous by cutting their power cord tether and keeping them in action almost continuously.  Think of little Roomba-like robots at home that don't need a charging station anymore.  Embedded computers don't only relate to robots but have all sorts of other applications like in home automation & entertainment systems.  PV built into these devices would not add any new load to the existing building.  Even better, these new devices could interact with energy management systems and even provide additional power back to the house when the devices aren't in use.  Quality of life continues to improve while our buildings continue to get smarter.

Whole building PV versus task-oriented, embedded solar?  Both have their applications and both versions of solar may end up working along each other very soon.

Solar panels are more than energy generation

Solar electric vehicle charging station at the OMSI in Portland, OR--shelter & power!

Electricity and thermal storage from the sun is pretty awesome, but solar panels can really offer so much more.  In certain parts of the world, covered outside areas are the norm to shelter people, animals, cars, or other equipment from the sun or rain.  Why not incorporate solar panels into the design to replace other building materials?  The structure is already budgeted and the incremental cost adder for the solar panels over the dumb panels would easily pay for itself from the locally generated clean energy.  As the weather continues to warm across the country and here in the Midwest, shading structures will continue to grow as a building design concept.  What a great way to add solar too! 

Chicago Botanical Garden Rice Center green roof with PV panels

Another example of the energy from solar panels being only one facet of its benefit to a building owner is with LEED projects.  Solar panels on a roof reduce the amount of roof space the project manager would need to dedicate to a green roof in order to achieve green roof credits.  Green roofs reduce water runoff, filter this runoff water, reduce building energy consumption, and the local heat island effect which effects the entire community.  Solar panels mixed with greenery are a win-win on all these accounts plus you get local energy production (EA credit 2) to boot.

Reducing expensive roofing materials with solar panels can pay for itself even before any energy generation 

One more example of solar being more than the sum of its energy production value is with slate and cedar roofs or other expensive roofing materials.  With these roof types, the installed cost per area of a roof integrated solar water heating collector could actually be less than the cost of the roofing material that is displaced--even before any energy savings are accrued.  I know that this is true for skylights with the daylighting and natural ventilation benefit being only a fraction of the total energy savings a building project with higher end roofing can see.

The more you look at solar, the more benefits you see, and the harder it becomes to justify sticking with old, polluting technologies.

Changing Times

Renewable Energy World had an article this morning that caught my attention.  The gist was that we have all the proof we need of man made global climate change and all technical tools we need to fix it.  Implementing these fixes won't reduce our standard of living; to the contrary, our collective way of life would be better in a clean energy economy.  For a number of reasons, however, solar hasn't gained the traction that it needs to be a robust industry and we are far from gaining the critical mass necessary for clean energy to dominate the total energy landscape.

Why?  I think the following reasons are part of the total answer:

• Fear of change in the popular mind
• Corrupt politicians on the take from lobbists
• Procrastination
• Nefariousness cabal of fossil fuel executives working for their own benefit to the detriment of society
• Ignorance of the complete cost-benefit profile of clean energy vs traditional energy
• Lack of inspirational leadership to point us down the right path
• Catch-22--we don't know how it will work because no one has implemented it and I want to wait for proof

We're at a societal crossroads now.  Economic issues are forcing our hand even before environmental ones have.  Either way, moving to clean energy is the right path as generation costs from dirty sources continue to swing widely and increment upwards.  Brace yourself for a rocky ride and don't fight the trends.  Flexibility is the key but so is recognizing that today's world will look vastly different than tomorrow's.

---

Come gather 'round people
Wherever you roam
And admit that the waters
Around you have grown
And accept it that soon
You'll be drenched to the bone
If your time to youIs worth savin'
Then you better start swimmin'
Or you'll sink like a stone
For the times they are a-changin'.

Come writers and critics
Who prophesize with your pen
And keep your eyes wide
The chance won't come again
And don't speak too soon
For the wheel's still in spin
And there's no tellin' who
That it's namin'
For the loser now
Will be later to win
For the times they are a-changin'.

Come senators, congressmen
Please heed the call
Don't stand in the doorway
Don't block up the hall
For he that gets hurt
Will be he who has stalled
There's a battle outside
And it is ragin'
It'll soon shake your windows
And rattle your walls
For the times they are a-changin'.

Come mothers and fathers
Throughout the land
And don't criticize
What you can't understand
Your sons and your daughters
Are beyond your command
Your old road is
Rapidly agin'
Please get out of the new one
If you can't lend your hand
For the times they are a-changin'.

The line it is drawn
The curse it is cast
The slow one now
Will later be fast
As the present now
Will later be past
The order is
Rapidly fadin'
And the first one now
Will later be last
For the times they are a-changin'.

- Bob Dylan The Times They Are A-Changin'

The Silver Tint of the Clouds of Doubt

There are dark clouds on the solar horizon.  Here are a few reasons why:

• All time low natural gas prices are driving down the cost of electricity and heating.
• Little public concern for climate change and zero political appetite for carbon mitigation legislation.
• Movement by utilities across the country to discourage solar PV interconnection.
• Economic depression with faint hope for the new construction market which is essential to a robust economy.
• Confusion in the public about the health of the solar industry due to high profile business failures like Solyndra.

This too shall pass as the famous proverb says because all material conditions, both positive and negative, are temporary.  All is not lost for solar.  We have a global energy market now and other parts of the world are adopting solar at such a clip that the US is going to benefit in the next phase of solar growth.

• The all time low natural gas prices hurt natgas producers and they are predicting rising prices due to production modifications and new markets for natgas like transportation.
• Solar provides a hedge against wild swings in energy prices--for many decades not just a few years.  Solar as a risk avoidance play is already viable around the world.
• Solar accounts for 4% of the electricity capacity in Germany but provides up to 50% of the load at key times during the year and day.  Germany has an inferior solar resource to anywhere in the continental United States.
• The cost of subsidized solar is rapidly approaching the cost of utility provided power.  Coupled with accelerating improvements in grid storage, utility barriers are becoming irrelevant.
• Solar of all types is very easy to install and requires very little training for professional contractors.  It will not take long to scale up solar once the market forces align.
• With nuclear energy on the decline, solar with grid storage is the only viable solution to provide stable power today and into the future.

When things go wrong, as they sometimes will,
When the funds are low and the debts are high,
And you want to smile, but you have to sigh,
When care is pressing you down a bit,
Rest, if you must, but don't you quit.
Life is queer with its twists and turns,
As every one of us sometimes learns,
And many a failure turns about,

When he might have won had he stuck it out;
Don't give up though the pace seems slow--
You may succeed with another blow.
Often the goal is nearer than,
It seems to a faint and faltering man, 

Often the struggler has given up, 

When he might have captured the victor's cup, 

And he learned too late when the night slipped down, 

How close he was to the golden crown.
Success is failure turned inside out--
The silver tint of the clouds of doubt, 

And you never can tell how close you are, 

It may be near when it seems so far, 

So stick to the fight when you're hardest hit-- 

It's when things seem worst that you must not quit.

- Author unknown

Energy Factor and water heating technologies

A different sort of green home

According to the US Dept of Energy's website, energy factor (EF) indicates a water heater's overall energy efficiency based on the amount of hot water produced per unit of fuel consumed over a typical day. This rating applies to a variety of water heater equipment: tank-style (storage), tankless/on-demand, and heat pump water heaters (HPWH).


Solar water heating has a very similar rating called the Solar Energy Factor (SEF).  Solar equipment is evaluated for thermal performance efficiency by an organization called the Solar Rating & Certification Corporation (SRCC).  The federal tax incentives for the installation of solar equipment are contingent on the solar water heating equipment having been evaluated by the SRCC.  The SRCC developed the SEF for the purpose of comparing solar water heating systems to a standard 50 gallon residential water heater in an apples-to-apples sort of way. Many natural gas utilities use the industry standard EF rating system to award rebates for high performing water heating equipment.  Since SEF is the solar equivalent of EF for a standard water heater, my view is that solar water heating systems that meet EF ratings for high performance equipment should qualify at a minimum for the existing utility rebate programs.


So how do different water heating technologies measure up with respect to energy efficiency?


Tank storage water heaters

Bradford White 40 gallon gas water heater

Typical residential storage water heaters range in size between 40 and 80 gallons.  This volume of water is heated up to the desired temperature (120 degrees F); the heating element or burner cycles on and off as a thermostat in the top portion of the tank detects adequate heat or not.  This is usually the least expensive water heating technology to install but is also normally the most expensive to operate. Recovery of the heat in the tank during and after use can be slower than with other water heaters which leads to the cold showers in high use situations.


EF rating for gas heated tank water heaters:

• Low efficiency -- < 0.62
• Medium efficiency -- 0.62 to 0.67
• High efficiency -- 0.67 to 0.82

EF rating for electric heated tank water heaters:

• Low efficiency -- <0.90
• High efficiency -- up to 0.95

Keep in mind that EF rating is only with respect to the energy efficiency of the appliance.  The electricity that heats the water in an electric tank model could be coming from sources with varying degrees of efficiency and environmental impact.

Tankless

Tankless water heater (top right) in conjunction with a solar water heater

Also called on-demand water heaters, these units heat water as it flows through the device.  They are capable of reducing water heating costs 10-20% due to the elimination of standby losses (constantly heating a tank of water even when no hot water is needed).  Tankless units come in electric, natural gas, and propane versions for different markets.  Not only are these a bit more energy efficient than tank style water heaters, they are also compact, wall mounted devices to save space in the mechanical room and they can provide almost unlimited amounts of hot water.


The EF rating for gas-fired tankless units ranges between 0.82 and 0.96. 


Heat Pump Water Heaters

From DOE

In a heat pump water heater, electricity is used to move heat from the air around the HPWH into the water tank versus directly heating the water with resistance coils.  Since the heat pump cycle can take a significant amount of time to heat or reheat a tank of water, electric resistance coils are included in HPWHs to augment the recovery of the water heating and thus minimize cold shower scenarios.  HPWHs can be very energy efficient and cost effective when the HPWH is operating in the heat pump mode; they revert to EF ratings of electric water heaters when the resistance coils kick in however.  Like with many things in the sustainable building world, efficient design is only part of the total picture.  How something is used in the real world effects its overall efficiency. 


EF ratings of HPWH in hybrid mode is 2.20 and fall off towards 0.93 in electric mode (average ~1.60).


Solar Water Heaters

In solar water heaters (SWH), the heat from the sun's radiation is transferred to drinking water during the day and stored in a tank of water for use throughout the day and night.  In homes where a 40 gallon tank water heater is appropriate, you'll find a 60 gallon solar storage tank. Because the amount of energy to move the heat from the solar collectors to the drinking water is minimal and the sun's energy is free, the operating costs of SWHs are the lowest of any water heating technology today. They are also the lowest carbon option when the system offsets fuel from gas appliances or electricity from coal-fired plants. SWHs have the highest upfront cost in the water heating space, but federal and state incentives exist to encourage their adoption since they provide a benefit to both the system owner and society as a whole.


Calculating EF from the SEF rating developed at the SRCC is done with the following equation: SEF x (1 - SF) = EF. SEF and SF (Solar Fraction) are calculations from the OG-300 report on each system found at www.solar-rating.org. EF ratings on SWHs range from 0.93 up to over 5.70 depending on the size of the system, location, and back up fuel option.


Summary
The less you pay upfront for a water heater, the more you pay over time.  As fuel prices of all sorts rise in the future, an investment in efficiency today will pay increasing dividends over time.

Talking solar at the CCGT

I spoke for the second time at the Chicago Center for Green Technology last Tuesday night.  The first time was last September and it went well enough for them to invite me back for another go at it.  My presentation covered solar water heating technologies in a broad way and has been set up to be a continuing education course for AIA architects.  Despite it being Valentine's Day, we had a rather large turn out with over 40 people in the audience.  The CCGT has been seeing strong attendance with all the their courses in this winter session.  I feel the general awareness level of the public is continuing to grow with respect to sustainable building practices and with solar technologies in particular.  The questions from the audience were more technical and specifically focused for projects that people are seriously considering.  I have even had 2 subsequent site evaluations from my talk for solar projects in Chicago from people interested in solar for their particular buildings.

 
I speak all the time about solar water heating and solar technologies in general so feel free to reach out to me about arranging a talk with your group!

Solar isn't a new idea

We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy — sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that.
                  - Thomas Edison

Why propane users need to investigate solar

Propane is a dominant heating fuel in rural parts of the US. Propane users typically purchase a large volume of fuel all at one time. It would not be unusual for them to have to write a check for $1250 1-2 times per year.  What this means is that like with a solar water heating system, they are pre-paying for the fuel they use to heat their home and domestic water.  Unlike with natgas and electricity customers, it's not great a leap for propane consumers to understand how a solar water heating system would benefit them in the long run since they can't spread payments out over time.  Additionally, propane customers tend to come from agricultural communities were communities tend to have a longer view of financial prudence.

To give a little flavor of the economics, I modeled a 2 panel, 70 gallon tank system pitched at 30 degrees facing due south in Des Moines, IA.  Using a solar water heater with propane back up tank, the homeowner would save about $450/year in water heating costs (using $2.50 per gallon for propane).  Switching to an electric back up tank with the same solar system, would save this homeowner about $500/year.  Either system would reduce the home's greenhouse gas emissions by about 1.3 tons of CO2.  Even with only the federal tax credit, this system would have a 10-year payback or 6.5% rate of return.  If propane prices go up to $3.50, the payback is cut to just over 7 years.  If your state has any additional incentives, you'll see paybacks as low as 5 years. 

A couple of good resources for propane related information would be Build With Propane and this propane supply outlook paper.

Save now and save later with solar. With a solar system, you fix your energy costs today and hedge against rising prices tomorrow.