While researching solar technologies, we at Green Compliance Plus heard from solar installers  who all seem to think that architects are hard to work with. So, we spoke with Fernando Valenzuela of Alter Systems in Berkeley about how to design a solar-ready home. Note that only about 5-10% of Alter Systems’ customers are owner/architect teams. Usually it’s the homeowners approaching them directly because they want to “go solar”.

So… why are architects hard to work with? “They have a groupthink… they like design, the look, but they don’t understand systems. They ask questions like ‘why can’t we use this roof’ without realizing that you can’t split up an array. Their projects aren’t always quick, either, and rebates that were designed for may be gone by the time the project gets through approval.”

Valenzuela went on to provide various design tips, as well as insights into new technologies, best-of-breed products, the difference between grid-tied and off-grid systems, costs and returns compared with conventional power, financing options, and the importance of grid parity.

Solar Design Tips for Architects

Consider building shape, roof planes, and orientation: With a remodel, people engage with an architect after the house is already built. It’s really best to take solar into account and design for it from the start. This may include choosing a lot or site that allows for a good solar orientation. Assuming that you do have some power to determine the shape of the building envelope, just make sure you include a nice un-shaded patch of south facing roof around 20 x 30 feet for your PV arrays. It goes without saying to consider proper solar orientation for the building, of course, if you have the option to do so.

Until recently, a single contiguous area was needed for solar arrays, and many products are still configured to work only if all the panels are installed together as a group. The panels should be tilted for maximum solar angle. Some panels lay flat and others can be tilted up; flat panels are aesthetically preferable and better for the neighbors’ attitudes.

Optimize roof tilt: The optimum tilt for the solar panels is your the latitude minus 15 degrees. In California, allow for a south or west facing planar area that is tilted around 20-22 degrees. Utility-scale projects and off-grid systems sometimes use solar tracking devices, but typically residential panels are mounted in a fixed position. The “solar window” is the maximum energy harvesting hours, between 9am and 3pm.

The sun's path across the sky changes according to season.

Assuming that you design includes panels that are built directly into the roof, your roof tilt will determine the panel tilt. “Not too steep, either, ” says Valenzuela. A 30 degree roof tilt is too steep – it’s much harder, and more dangerous, to install the panels. “It works your abs and butt!” laughed Valenzuela. And it’s not exactly “green design” when crews get injured, is it?

The roof tilt also depends on whether you have a grid-tied or an off-grid system, according to Valenzuela.

• Grid tied should be your latitude minus 15 degrees. Grid-tied systems are optimized for summer, because that’s when you’ll get the most energy out of the system, and thus you’ll get more money back at the end of each year.
• Off grid, on the other hand, should ideally be your latitude plus 15 degrees. For off-grid you maximize for winter, because you need the system working even in the worst-case scenarios so that you’re not left in the dark. Basically you want to make sure the system will produce in the winter months.

Allow space for conduits: If solar power is an afterthought, then you may have a visible exterior conduit, which can be less aesthetic than building it into the wall. If you put the conduit under the sheetrock it won’t even show on the outside. But even if you’re not installing solar today, you can accommodate future solar in the design.

Left, a typical retrofit requires routing the conduits wherever you can. Right, allowing a place for solar conduits that's built into the house allows flexibility for future solar.

Be careful with vent placement. “Don’t put vent pipes in the middle of a rooftop solar array. If the pipes stick up too far, they’ll get in the way of the PV panels.”

Make the roofing strong. Roofing should be 2 x 6 or 2 x 10 at 16″ on center for strength. Modern codes want 2 x 4 at 24″ across to conserve materials. If the span is too long, however, this doesn’t account for the weight of the people walking on it to do things like install solar panels. For this purpose, spans over 8 feet need thicker rafters. “We do a lot of retrofits,” says Valenzuela. “Old buildings in Berkeley for example are often 2 x 4 at 24 off center. For these, we may have to put in a brace.”

Keep basic sizing guidelines in mind. The amount of surface area you need for your PV panels depends on how effective the panels themselves are, and how much power the house requires. A rule of thumb might be 500-600 SF of roof (or other area) for the solar array to generate 5 – 7 kW. This covers a lot of places, even desert climates. “Even in the hotter parts of California, with heavy air-conditioning loads, it’s not too far off base,” according to Valenzuela.

Understand the racking systems. It’s good to understand how racking systems operate. “No roof penetrations” are needed. In the future, each panel may come with an independent energy panels with built-in inverters. Innovations include reduced installation time and cost.

Process

Choosing Your Solar Companies: A solar systems company is essentially a contractor/consultant who supplies, specifies, and installs systems. “If your client wants solar power for heating, cooling, electricity, or water heating, then you as the architect will need to establish a good relationship with a company that you can rely on to supply a well-designed system that is appropriate for the programmatic requirements of the home.”

“Try to work with a few solar systems companies that you know well, to get standard products and sizes for components. But don’t rely on just one company, because some companies are over-scheduled right now and orders are going unfulfilled.”

How Long Does It Take? Allow a month turnaround including all permits and paperwork such as rebates.

Customer Experience: So what happens when someone comes to you and says they’re ready to go solar? Here’s what your clients can expect.

1. Site evaluation. The solar consultant will most likely want to visit the house to inspect the roof area, shading, and electrical box. Some houses just aren’t suitable for solar. “Usually it’s a mounting problem,” says Valenzuela. A general rule of thumb for say a 1,200 – 2,000 SF house is to have flat or south facing roof around 20 x 30. Using micro-inverters helps reduce the amount of roof area that you need (read on for more information).
2. Proposal. Assuming the house will support a solar system, the owner gets a price proposal. “I have to ask why they’re doing it to figure out if it’s off-grid, grid-tied, or hybrid system. If they sign off, the paperwork starts.”
3. Permits and Rebates. Local permits for installing a solar system can take as little as a day or up to around 2 weeks depending on locale. The paperwork for tax rebate programs takes 2-3 weeks.
4. Installation. Alter Systems takes 2 days to install, but schedules for 4 days to allow for contingencies such as rain. The owners or occupants can continue to use the home and live in the home while the installation is ongoing.

Grid-Tied and Off-Grid Systems

One basic decision the owners must make is whether to tie their new solar arrays int the power grid. Grid-tied and off-grid systems are totally different animals in some important ways, but as solar power gains mainstream acceptance, it must also be able to integrate smoothly into mainstream infrastructures as well.

• Off-Grid systems are the classic “1.0″ of solar renewable energy. Although they tend to be associated in the U.S. with environmental activism, survivalist movements, and early-adopting technology buffs, they’re also essential in parts of the world where a centralized power infrastructure either doesn’t exist or isn’t reliable.
• Grid-Tied systems are mainly intended to reduce or eliminate energy bills, as in Net Zero homes. It’s a more mainstream market than either the early adopters or the green contingent. A main motivation is likely to be cost savings.

Although grid-tied systems are a newer concept, they are likely to be the wave of the future in industrialized countries. The components of a grid-tied solar system are the panel arrays, a power inverter to convert the direct current generated by the panels into the alternating current used by household appliances, a manual power disconnect, and of course the utility company’s usual infrastructure: the meter and switch box.

A grid-tied system is simple and straightforward. There is no need to store power onsite. Power generated is fed directly back into the grid, and home power needs are drawn also directly from the grid.

An off-grid system has more components, because of the onsite power storage requirement. In an off-grid system, the solar arrays feed into a combiner box which balances the inputs from each array. The combiner box combines or branches together the PV arrays/modules and then takes all the power through one set of leads to the charge controller. The controller makes sure your battery is charged correctly, and prevent over-charging.

The advantage to this type of off-grid configuration is the ease with which you can add supplemental power-generation systems such as microhydro or wind turbines. The goal of an off-grid system is to keep the batteries fully charged at all times. If there’s a grid tie-in, the battery won’t “sell” back to the grid unless it is already fully charged.

Which configuration you choose for your solar system depends on the reason why you’re going solar in the first place. Homeowners typically adopt a grid-tied system to save on energy bills, reduce their carbon footprint, and perhaps to show off to their neighbors. Valenzuela cites an estimate from the Journal of Assessors and Appraisers that for each dollar you can shave off your annual home operating costs, you add $20 to the property value.

According to Valenzuela, based on his experiences with his own customers, homeowners might choose off-grid because they’re in a remote area, and either it’s too expensive to bring the grid out there, or it exists but is not completely unreliable. “Some people do it because they hate public utility companies just on principle,” notes Valenzuela. “They’re also more likely to be DIY types who are comfortable assembling their own systems,” he adds.

An off-grid system includes an onsite storage battery. It's designed to be self-reliant. The homeowner can add a grid-tie option as shown above.

So what are the pros and cons of each type of solar configuration? Grid-tied systems require less equipment and employ simpler configurations; on the downside, they’re limited based on inverter sizes.

With off-grid systems, it’s easier to add supplemental renewable-energy systems on the side for things like wind or microhydro.

It's easier to add supplemental power generation systems to an off-grid system with its own battery storage.

Off-Grid for Villages: A typical residential home might need a 6kW system. For sites such as an army base, a remote ranger station, or a farm with multiple buildings, a system called AC coupling can deliver 20 kW or more. Basically it’s a way to create your own micro-utility company, and collect power from solar arrays on several buildings, using one central inverter (such as the Sunny Island off-grid inverter from SMA Solar Technology) and a central storage area. “This type of installation is very useful in places like the Caribbean, island countries or places without any infrastructure,” says Valenzuela.

Could you implement something like that in a city neighborhood, I wondered? A residential collective of some sort, for people who live in urban areas but still want to have totally independent self-generated power, and who want to pool their money to invest in economies of scale? “You’d have to do all your own wiring,” Valenzuela responded. “They’d have to be fairly close together.”

Well… with the geek factor in this area of the country, I wouldn’t be surprised if it’s already happening. After all, if a few homes drop off the grid on a single city block, how would we ever know?

Solar Grid Parity

I didn’t even know what this was, but with all the talk about the ROI of solar systems vs. fuel cells vs. high-efficiency but conventional systems, it’s a very important concept. Solar grid parity is a tipping point in the energy marketplace when the cost of energy production for solar power will be equal to or less than the cost of generating conventional, fossil fuel-based grid power.

A common comparison is dollars per watt or cost per kWh. U.S. average power prices for last year ranged from 5 – 15 cents per kWh, averaging roughly around 10-11% (businesses were 1 cent cheaper).

This number includes upfront investment in equipment although of course there’s debate over how to calculate it and when this momentous day will actually come. 2012 seems to be a common guess, although coincidentally that’s also the end of the world, according to the Mayan doomsday calendar).

Prediction: “a number of solar companies will hit a long-pursued industry target of $1 per watt by 2012.”  This “race towards $1 per watt” means that “within a few years solar panels will be able to generate electricity cheaper than the grid in many regions of the world.” (Sunnier regions have a bigger solar payoff, not surprisingly.)

Another claim is that we can reach 2012 grid parity in “almost half the US” and he also notes that there are several ways to calculate grid parity.

Even 4 years ago, solar was still pooh-poohed as a boutique technology for wealthy do-gooders or conspicuous consumers. But that was before tax rebates and stimulus dollars made it easier for new owners to “green” their homes. Other factors include improved component efficiency and a wider array of creative financing options such as these options from SunRun to purchase solar power as a service, to lease the equipment to the owner, or to help owners seek solar financing through local municipal programs.

So, is it a sure thing that in 2012 we’ll all be putting PG&E out of business? Doubtful, but there’s definitely a sense that price parity is coming, it’s just a matter of when. For example, higher interest rates could hurt financing, and if grid prices fall, parity won’t be reached nearly as soon. For those who prefer to focus on equipment efficiencies, there’s a rather geeky engineering article from BP Solar that discusses current and future efficiencies, including emerging new technologies such organic photovoltaics and nanocomposite solar cells.

The $1 per watt number is disputed as overly simplistic on one investor blog: “PV’s competiveness with the grid varies wildly based on the region… The idea that module prices need to come down to $1/W for solar to be competitive is misplaced at best” because “PV is already at or near parity with the grid in a number of markets”. This blog also includes a good discussion of calculating the cost of various types of conventional power, including nuclear.

Solar Financing Innovations

For homeowners who want to finance their solar installation, three good sources are:

• Tax rebates
• Municipal funding options through property taxes
• Bank loans

In the second case above, this is a plan being adopted in some localities such as Santa Rosa. Basically, the city obtains the funds for solar installations at a very low interest, say 3%. The city then loans it out to homeowners at a slightly higher but still reasonable rate, say 7%. The owner then pays back the loan in the form of an extra property tax surcharge every year. If the house is sold, the new owner is responsible for continuing those payments as part of the home’s property tax bill, and the new owner of course enjoys the reduced energy bills in the meantime.

“Some owners just pay for it with a credit card,” said Valenzuela. I can’t imagine plunking down $35-$60,000 on my card but then again, I can’t imagine watching the national average of television, either. “Every dollar decrease in operating cost adds an extra $20 in property value,” said Valenzuela, “but equity is fake money. So, we don’t include this increased equity on our cost/benefit analyses that we show customers in our proposals.”

New Solar Products

During the course of our conversation, Valenzuela mentioned some of his favorite new solar technologies. In no particular order, here they are.

Solar forced air heaters. These devices are installed on a south-facing wall or roof and are best used as a complement to other heating systems, a boost but not a replacement. They’re small and relatively efficient, at least compared to PVs. A single 8-foot panel is enough to heat a small room. They use no fuel and have no moving parts except a fan to draw cold air into the panel and push heated air out directly into the room. They don’t work as well on cloudy days, obviously. And you don’t even need fancy PVs or heat collectors: here are some ingenious DIY solar air heaters made from recycled aluminum cans.

This 8-foot solar wall air heater from ClearDome Solar in San Diego can heat up to 500 SF of residential space.

Micro-Inverters. Green Compliance Plus has mentioned the breakthrough of micro-inverters in a previous post – basically, by having separate inverters for every PV panel in a solar array, you can harvest more energy because shaded panels no longer bring down the performance of the entire array. One maker of micro-inverters is Enphase Energy. Valenzuela waxed almost poetic about Enphase products: “At the recent Green Building Expo, their booth was mobbed while the big players were empty!”

FLEXpower ONE Off-Grid Solution. Valenzuela made special mention of one particular product from OutBack Power called the FLEXpower ONE. He recommended this for total off-grid systems including smaller installations such as boats.

Xantrex XW Grid-Tied Solution. The Xantrex XW from Schneider Electric is recommended for homes that are grid-tied with a battery backup. “It’s not quite as flexible as the OutBack for very small installations, but it’s easier for designers, because it’s a high-quality product and you can scale it up,” says Valenzuela.

But what should architects really know? “Use Enphase!” says Valenzuela.

One of our Title 24 clients, Okamoto Saijo Architecture, recently completed a  $50M retrofit that included creating a 900-kW PV system that is currently one of the largest affordable-housing solar installations in the world. We interviewed one of the principal architects, Eric Saijo, about how the Crescent Park project went from his perspective. He was actually quite happy with the outcome, and after 4+ years of budgeting, negotiating with utilities, the project is completed.

Crescent Park, an affordable-housing solar retrofit by Okamoto Saijo Architecture.

How were you selected?

In the last 12 years we’ve done lots of affordable housing rehabilitation projects. In this day and age people get put into certain categories. We’ve developed a reputation.

Eric Saijo and Paul Okamoto of Okamoto Saijo Architecture, at one of their own project sites

It’s less glamorous, but that’s OK. This client had been working with another architect and the project got put on the back burner for half a year. In 2005, they came to us. We spent 2 years in design and documentation to figure out the project scope.

How was scope determined?

Identifying the budget is always a challenge. They had a wish list of many items, including PV for 100% of electrical needs. We did feasibility studies to analyze whether they had the budget for all the things they wanted to do: update kitchens, flooring, waterproofing. The solar portion was only one aspect.

You did a lot of analysis in addition to design.

We worked hand in hand with our contractor (Brandon Slater of West Coast Contractors) from Day 1 on pricing and budget.

What would you do differently next time?

A better question might be what have we learned? Let’s talk about this instead. We learned more about handling the specific challenges of pulling off a PV installation in a 40-year-old multi-building complex.

Okamoto Saijo Architecture has done "green" private residences as well as sustainable public housing.

We started off with plans for 100% of onsite electrical needs generated by PVs. Our solar engineer did a layout showing where we could put panels on all roofs, taking tilt and orientation into account for each building. We also had an idea of the number of kWh that we needed to generate. Then we could look at all the other constraints.

What were the other constraints?

Not enough roof area on the existing buildings, and existing building systems that were not designed for the structural loads of the panels and the installation process.

Are solar panels really that heavy?

No, but retrofitting existing buildings triggers all sorts of re-analyses, and one of these is to re-analyze for seismic load. Any building that’s 40 years old won’t pass today’s seismic code requirements. And any increase in load over 5% triggers this seismic analysis… it’s a huge limiting factor.

Most PVs get installed in a design-build fashion.

When installing panels, there should be no live load on the roof where the panels are… adding even a minuscule amount of weight can be a problem sometimes.

What was the problem with retrofitting to use existing equipment?

How to make the most of the existing electrical service equipment in a retrofit! The simplest thing to do for an individual building is to install a large PV system and replace all the service equipment and tie in the PV to the entrance panel breaker.

Connecting those beautiful photovoltaics to the public utility's metering and grid system can be a "non-trivial exercise".

The electrical code is written in such a way that PVs are considered a “load” meaning that you might have to up-size the service equipment. The secondary field lines from PG&E, with extra runs to each building, for 24 buildings on 6 acres… this becomes a huge cost.

However, the electrical code does allow for line-side tap between the meter and the main shutoff switch. The equipment is now 40 years old which the code still allows, but it is physically difficult to implement line-side taps. We had to persuade PG&E and the head building official to conceptually approve it.

The larger buildings had enough space in their service equipment to clamp onto existing conductors when we needed to do that. We had to modify the charge condition meter main shut off and route it through a new gutter. We could do new tap here. and then clamp to conductor.

UL certification was another issue. The existing equipment, being 40 years old, wasn’t UL fabricated. Small enough to service meter and switch board were separate pieces of equipment. When the contractor, the electrical building inspector, the electrician, and the solar engineer got together – it was a tense moment!

When architects and building inspectors meet…

The next challenge was getting our systems approved by PG&E. You have to get approval from your local utility in order to submit for solar tax rebates. A 900 kW system like this one must undergo review at PG&E’s engineering department. They analyze their own infrastructure, including their transformers and underground conduits. In this case, PG&E’s equipment was also 40 years old, and perhaps built to prior standards. It took them quite awhile to analyze our proposal.

At first, they rejected it and wanted us to pay to upgrade all the transformers serving the complex. This was due to a loophole in the agreement for rebate systems for PVs, which allow the utilities to charge the client for these upgrades.

But if the power is generated onsite, why do you need those transformers?

In the middle of the day in a residential complex, power will be flowing out towards the grid. Changes to the photovoltaic systems had to be calibrated on the utilties’ side as well as ours. They had to change their meters so they could spin backwards.

Is that a smart meter?

No. A smart meter is one which is read remotely. [Communication is essentially what makes a smart meter more intelligent than a dumb meter]

Does PG&E do enough to support people like you?

There are people in various departments who did. The engineers really got behind us and worked with us to MAKE it work. Then there are other departments. All of them get delayed for a number of months without clear explanation. It could just be under-staffing.

Here’s an example of the type of problem we had to solve together with PG&E engineering… in one area of our project, there were 5 buildings served by one transformer. At first the told us that we had to pay for a new transformer, as well as pay for new primary and secondary feed lines – this would cost $200K.

Naturally our client wasn’t happy. PG&E countered that they were concerned that the kW would bump up the voltage above what they’re legally required to keep it under. Then they said, “But.. if you set the trip point on the inverters down, then we’ll approve.”

Inverters are normally set to 132V and they wanted us to set them at 127V. The PG&E grid is 120-122V but it just happens to be high in this particular location. As we installed systems in those 5 buildings, the inverters started to trip off. We’re still negotiating with PG&E over what to do.

What would you do different?

I wouldn’t accept a trip point! It was a sign that PG&E has real concerns about its own systems, that they were worried about the potential for voltage to increase too high . Our solar engineer had never run into that before. It was a real learning experience!

Even a genius can have a learning experience.

At this stage, our client didn’t know yet how much financing they could get. The budget was still in flux, and they really weren’t willing to accept sudden new costs. Especially in large renovations, you have to hold a large contingency fund; with our project, those funds are now available for post-construction.

What do the residents think about it?

Affordable housing is a very complex thing in our society. These are extremely low-income people. I didn’t have much contact with them but my sense is that they are appreciative of the renovations that included window replacement and other building improvements which improved their comfort and quality of life.

Another affordable housing project from Okamoto Saijo Architecture, PositiveMATCH is an adaptive re-use of a historic building in San Francisco, serving women with HIV and their children.

The buildings were made more airtight, with better insulation, new windows. And… cleaning the duct work after 40 years most likely improved the air quality.

Drainage for the entire site was improved. It’s very close to the Bay, with a high water table, so flooding is a concern. The storm drains were constantly backed up prior to the renovation, and ground floor units had water infiltration. All of these measures made the units more comfortable.

Another private residential design from Okamoto Saijo Architecture, a passive-solar farmhouse in Napa, CA

We also worked with the client to improve the visual appearance of the buildings. New paint schemes, and individual colors for each building. Before that, all 26 buildings on 24 acres had been colored the same. How monotonous!

Of course the resident’s don’t pay their own electric bill. That’s usually the thrilling part for homeowners is seeing their utility bill reduced. In this case, our client financed the PVs because they also pay the utilities.

Financing was through bonds. Our client was not the original developer. The project was originally built by a market-rate developer together with HUD. Our client bought it later, around 20 years ago.

Renewable energy companies must be doing well these days. Between green stimulus dollars, soaring energy costs, recession-weary homeowners, and increasing public demand for clean energy, it seems like homeowners would be queueing up for the next Net Zero Energy conversion. And those who can afford the initial outlay probably are. But what about the rest of us who don’t have $35,000 just lying around?

We spoke with Kent Halliburton of RealGoods Solar about the state of the art in solar technologies, focusing on products that are available today. “Here’s a stat for you,” he said. “At a recent solar symposium, it was said that 92% of customers want solar energy but 88% don’t know how to get it.”

Hmm… well, if I wanted a new furnace, I’d look in the papers for contractors who installed the type of system I wanted. So what’s stopping these people from typing “solar installers” into their favorite online search engine?

Maybe what he meant was they don’t know how to PAY for it. And until now, there weren’t good financing agreements that allowed people to pay as you go. “People talk about solar price points as if it were a deterrent,” Kent said. “People aren’t as upset about the price point for vehicles like a Toyota or a Chevy, because car dealers sell in terms of monthly payments, not total system cost.”

Solar as a Service

“We have a new financial product offering solar as a service,” he explained. Instead of having to purchase their own solar system, the homeowner contracts to have the system installed and maintained by a third party – in this case, Sun Run, our financial partner. The equipment is actually owned by Sun Run and is sized to meet about 80% of the home’s total projected energy needs. The other 20% is purchased as conventional power.”

In the arrangement described by Halliburton, a homeowner signs an agreement through Sun Run to purchase from Sun Run all the power generated by the solar system, locking in a fixed rate for the next 18 years. The homeowner also pays a certain amount down, anywhere from $0 to around $2,000. This pricing is a little different from the more familiar metered pay-for-what-you-use model, since the homeowner commits to purchasing ALL power generated by their solar system system, whether or not they use it. (Unused power is usually fed back into the power grid.)

System output is somewhat variable depending on the weather, and is usually estimated over a year’s time to average out seasonal ups and downs. The systems come with site-specific production guarantees. In any given month, the homeowner might under-produce and end up using a small amount of conventional power – but in the following month, a span of sunny days might generate a solar surplus that would then act to reduce the amount of kWh billed by PG&E at the end of the year.

A More Efficient Home Needs a Smaller Solar Array

Since the homeowners are already committed to paying for the output, the thinking is to size the system a little on the small side so they use up what they’ve already paid for. A conservatively sized system also encourages homeowner to reduce energy consumption. “For every dollar you save on energy efficiency, you can save $3-$5 on your solar system.”

Additionally, PG&E’s tiered rating structure means it’s cheaper to buy power from them at the lowest tiers – but not at the upper ones. And if the system produces more than they need, they’ve already paid for that portion of the power and it’s still overall cheaper than PG&E rates.

“But don’t wait to energy-proof your home first and then get a solar system, because it’ll take you months and during that time you’ll still be paying for conventional power. We encourage people to do everything possible to their home while installing the solar system.”

Latest Solar Technologies

So what’s the state of the art in solar technology? According to Halliburton, there remain two main technologies: silicon-based panels, and thin film panels. The tradeoffs are cost and efficiency – thin film is cheaper but less efficient, so you need more of it, and more roof space, to generate the same amount of power. So, what’s the best money can buy as of today?

• Silicon-based panels currently cost around $2.25/watt and are around 16% efficiency. That means that 16% of the sun’s rays that actually fall on that panel are converted to usable electric power.
• Thin-film panels are around $1.50/watt and around 8% efficiency.

[Note: These prices quoted by Halliburton are for the panels, not total installed system cost. On Sun Run's site the price is listed as closer to $8/watt.]

Large commercial applications can afford the space for huge arrays, but thin-film solar products can be flexible and more adaptable to portable off-grid field shelters.

What’s the most efficient, top-of-the-line system that’s available today? “SunPower and Sanyo both make products that are around $1 per watt more expensive than average. They’re around 17.5% or 18% efficient. You have to watch it though, because some manufacturers use a measure that is per cell, not panel efficiency. By contrast a so-called middle-tier ‘average’ system might be more like 14.5% to 15% efficient.” Today’s thin-film solar products top out around 9% efficiency.

“Silicon-based panels are better for residential and small commercial applications,” said Halliburton. Larger commercial applications have the real estate to install larger arrays of thin-film panels, but smaller buildings might need a smaller footprint and thus a more compact and efficient system is better, even if the initial costs are higher. “The most common choice is definitely the middle tier.”

Solar Inverters: The Hidden Factor

But even more important than the panels themselves are the inverters, and that’s something most people never think about. An inverter is necessary in order to convert the DC power produced by the solar panel into the AC power that’s used in a home. In the past few years, advances in inverter technologies and configurations have further improved the potential yield from an otherwise average solar array.

Halliburton described how inverters function. “The emergence of micro-inverters has done more to change the solar landscape even than the incremental gains in efficiency that we’ve seen over the years. In the older systems, there was one inverter for all the panels, but with a micro-inverter, you can have one inverter for each panel.”

To get an idea of why this is so important, consider a 4 x 4 solar array of 16 panels on a roof that is partially shaded at certain times of day. If even one of those panels is shaded, then its output is reduced – and the inverter can only gather the output from all the panels at the lowest common denominator. “With a single inverter, the weakest link brings down production for the entire array.”

With a single inverter, the two shaded panels will bring down the performance of the entire array during the time that they do not receive full sun.

By contrast, an array with micro-inverters is less sensitive to partial shading. I observed that this sort of thing must be a no-brainer for an engineer who already knew how the inverters worked with solar arrays.

With separate inverters, each panel is always producing the maximum possible based on the available light that reaches its surface.

Looking Ahead

What’s the state of the art now as compared to 5 years back? “Gains are incremental year by year,” said Halliburton. “For example, 5 years ago we had a 168-watt product from Sharp. That same product today is 198 watts. We try to avoid the ‘Apple syndrome’ where users hold off on buying a new computer because they’re always waiting for next year’s model.”

Halliburton stressed that homeowners didn’t need to wait to install a solar system, even if they were also planning other home improvements to increase building efficiency. Although they might think that a more efficient building with all the latest energy-scrimping appliances will need a smaller solar array, the systems are already sized with this possibility in mind, and in the meantime, why should the homeowner continue to throw away money on the electric bill for all the months it’ll take to complete their energy remodel?

Where do you see solar technologies 5 years from now? “It’ll become more ubiquitous, and continue to make incremental gains. I don’t see any silver bullets, meaning a brand new technology that’s disruptive in the market. In fact, I think the real change is going to be in education. People judge energy consumption based on the number of switches that they flip. They don’t understand what they can’t see. Customers will need to educate themselves and become more conscious of their consumption habits.”

What About Renters?

What’s really stopping people from buying solar systems? Well, not owning your own home is one barrier, although an arrangement called Virtual Net Metering can allow someone who lives and rents in one area but owns property in another town to install a solar system on the property that they own, and have the power it produces be counted towards the energy bills for their rental unit elsewhere. 

The Solar Homeowner Experience

What’s the solar homeowner experience? Do they notice any difference, or do they need to do different sorts of maintenance? Do they ever run short of power? Does the homeowner get an energy bill every month like the rest of us? 

“Other than washing the dust off the panels every so often to improve their performance, not much. They still get monthly statements. There’s online monitoring and automatic billing. The inverters might need to be replaced sometime between years 12 and 17; the panels themselves are guaranteed to produce up to 80% of their original efficiency even after 25 years.”

Visibility into System Stats

How much visibility do homeowners have into how well their system is doing? “The inverters tell them how much power their system is producing, and with online monitoring, they can see all the stats easily.” 

What about whether their panels are really operating at maximum efficiency? “Most customer don’t care about that level of detail, but one could install sensors to measure solar irradiance levels if someone really wanted to know that.”  What they typically get is a quote on what their system will produce on a monthly basis. 

The early adopters were more likely to be gearheads and DIY types with the engineering skills to really prove and verify their own systems. As solar power gains wider acceptance, people are more willing to trust it the way they would with a new conventional furnace unit.

Financing the Future

The impression I had after speaking with Halliburton, especially about the Solar as a Service arrangement, is that innovations in pricing structures and financial incentives will be as challenging – and as necessary – as any engineering improvements to the products themselves. RealGoods has been around for 31 years, in fact RealGoods sold the first solar panel in the U.S. back in 1978. They’ve installed over 5,000 systems to date, with around 200 customers signed up for the Solar as a Service plan that was introduced only a year or two ago.

It’ll be interesting to see where things are, even two years from now.

Nearly every week, we are asked why Title 24 does not give credits for electric water heating if that electricity comes from solar or other self-generated power. In fact, it seems that many of the renewable energy developments occurring now are not fully recognized in Title 24, not even in the 2008 code. We’re in the position of telling people that their homes, which are designed to consume very little conventional power, may have trouble passing the Title 24 code if those homes rely solely on solar electric for all their home power, heating, cooling, and water heating needs.

So why does T24 continue to penalize electric resistance heat and water heating in solar homes? Why does T24 not give credits for self-generated power (geotherm, solar, wind, other)? And why can’t our utilities buy back excess power from customers who generate more than they use? Wouldn’t this help to reduce California’s grid load, save California homeowners money, provide entrepeneurial opportunities, and reduce American dependence on foreign oil?

Title 24 History

California’s energy standards were originally mandated in 1974 by the California legislature, through a piece of legislation commonly known as the Warren Alquist Act. This act created the California Energy Commission and authorized it to develop and maintain energy efficiency standards for new buildings, and it specifically requires that these standards be cost-effective “when taken in their entirety and amortized over the economic life of the structure.” (Title 24 2005 Residential Compliance Manual)

According to the Title 24 2005 Residential Compliance Manual, Title 24’s stated intentions are the following:

• Save homeowners money
• Keep homes affordable
• Reduce strain on the power grid during peak times by reducing demand
• Stabilize California’s economy by buffering against sudden price increases
• Comfort (poorly insulated and drafty homes with oversized systems that cycle on and off are less comfortable)
• Reduce environmental pollution
• Reduce carbon emissions

California Energy Commission’s Response

I started with the California Energy Commission, which is responsible for creating and updating the Title 24 energy code. Why would the code ignore the potential of self-generated power to reduce demand for conventional power when our grid is already fragile? I spoke with Mazi Shirakh, P.E., M.B.A., a Senior Mechanical Engineer who serves as the Project Manager for Building Energy Efficiency Standards at the CEC, and who is also the Program Lead for the 2008 Standards update. Mr. Shirakh outlined the reasoning behind Title 24’s approach to alternative energies. (It is normally the Commission’s policy that individual staff members should not be named in articles and blogs, but in this case they’ve agreed to allow us to attribute directly.)

“The reason is that up until now, alternative energy technologies were too expensive when compared with more traditional energy-efficiency measures such as high-performance windows or air conditioners. While their costs remain high, PVs cannot demonstrate cost effectiveness as required by the law. We recognize that this is changing,” explained Shirakh.  “PVs are still expensive, costing around $8/watt. To install a 2Kw solar system costs around $16-$20K, whereas you can get a high-efficiency furnace or air conditioner for a lot less than that. However, the price of PVs has been steadily decreasing since the beginning of 2009. Assuming that this trend continues, there will be more possibilities for PVs in the future rounds of Standards. At around $2 or $3 a watt (including incentives) PVs would be much more competitive with traditional efficiency measures.”

Shirakh mentioned incentives such as the New Solar Homes Partnership, and I pointed out that such programs have nothing to do with Title 24’s internal scoring. If the intent is to reduce the load on the grid through less use of conventional power, why should an electric water heater that runs from PVs be scored the same as an electric water heater that runs on conventional power?

“The building must meet a certain efficiency levels first before PV or other on-site systems are considered. If we didn’t do this, there would be nothing to stop someone from building an inefficient structure and just slapping an array of PVs on the roof instead of other efficiency measures such as building insulation. And there’d be nothing to stop the owner from ripping out those PVs later on and running the building solely off the grid.” he replied.

OK, I’ll buy that for a dollar.

Alternative energy contractors are less inclined to accept this argument without comment, however. “That’s a spurious argument, in my opinion. Who’s going to take a building with a functioning solar system and rip it out?” said Gary Gerber of Sun Light and Power, a solar systems designer and installer. Another alternative-energy contractor, Greg Kennedy of Occidental Power, speculated that it was about centralized versus decentralized power networks. “Utilities are building big centralized power plants, with solar installations far out in the desert and then transporting the power over long distances. If that power were generated more locally, less of it would be lost during transmission. It’s really about who’s controlling the cash register.”

In a subsequent exchange, Shirakh clarified CEC’s position regarding Title 24’s approach to self-generated power: “Allowing proper credit for solar assisted electric water heating is one of the goals of the next round of Standards (currently known as the 2011 Standards). However, we need to be careful about how much credit is given to onsite generation measures; we still want to encourage buildings with efficient envelopes, mechanical, water heating, and lighting systems, even in the presence of PVs and other onsite generation systems. In addition, an energy efficient building will require a smaller solar system (less costs) and provides more comfort to the occupants. It should be also be noted that the Standards do allow a substantial credit for solar thermal water heating which can be combined with either natural gas or electricity. This is a mature technology and is widely available within the State.”

Shirakh was not familiar with fuel-cell technologies such as ClearEdge Power’s product offerings. However, he assured me that if we did any Title 24 documentation for a project that used them, we could contact the CEC for assistance.

Does Renewable Energy Comply with Title 24?

So, how hard is it to get a net-zero home to comply with Title 24? “Most are quite easy, because they are relatively efficient buildings already,” responded Dave Knight of the Monterey Energy Group. “The coastal areas and the hills are OK, but it is significantly harder to get a net-zero home to pass in Central California. California’s central climate zones are very hot, and the A/C load kicks in.”

Knight added, “From the very beginning, Title 24 mandated that solutions be cost-effective. In the past, some systems such as solar thermal could supply 80-90% of a home’s space heating load, but were seldom cost-effective, and it was complicated to predict how they would work. But they’re not looking at the current prices or the latest incentives. In the last few years, the prices of solar PV have dropped by 20-25%. So there’s three things coming together now: more efficient buildings, lower PV prices, and new tax incentives.”

So What Can We Do About It?

“The Grid-Tied Solar Electric home that we discussed at the AIA in San Francisco a few weeks ago is unbelievably simple, reliable, and predictable. And it’s cost-effective today. No matter what our clients’ motivation is, whether it’s reducing carbon emissions, saving on energy bills, or reducing dependence on foreign oil, there’s an incentive for them to convert their home to GTSE,” Knight responded, and went on to urge the design community itself to take on the task of change.

“I think the AIA should take the lead in building and promoting Net-Zero Energy homes. I mean, a LEED certification can cost six figures and require what seems like thousands of meetings. By promoting Net-Zero Energy homes, the AIA could push their own agenda without waiting for the CEC to catch up.”

Why Can’t We Sell Back to the Grid?

What about people selling their excess power back to the utilities like they can in Germany? “There’s a difference between a feed-in tariff and selling back the excess through net metering. A feed-in tariff guarantees or fixes the rate at which power is sold back. Net metering simply measures how much energy is used versus replaced. But, any excess you produce is a gift to the utility,” said Gary Gerber.

“There are actually several bills that have come up for this in the past few years, including one that’s on the table right now. Allowing PV owners to sell excess would offer several benefits. For one thing, it promotes a cleaner environment because it uses no fossil fuels. But just as important is PV’s potential to reduce peak loads at the hottest times of the year, since peak cooling times are also when the sun is strongest.”

The Politics of Renewable Energy: Left and Right

Politically, there’s an unspoken divide between liberal and conservative approaches to power generation. Conservatives tend to push for nuclear power and offshore drilling, whereas liberals are more likely to promote clean solar energy and lifestyle changes. “We don’t care, it’s about what really works,” observes Green Compliance Plus founder Mark English. “Knee-jerk ideologies are not useful. There’s nothing inherently wrong with nuclear power. Look at the French and Japanese nuclear power models.”

There have been a few reported accidents, and safety is a major concern for both operation and waste disposal, but overall France seems to have a good nuclear energy model. A formerly oil-dependent nation, France invested heavily in nuclear power as a response to the 1973 oil crisis – now they actually EXPORT power. (Perhaps rather than dismissing it out of hand, we could seek to enforce accountability by requiring all nuclear executives and managers and their families to reside within a mile of their own power plants?)

Having said that, the ideological debate does tend to polarize along party lines. Solar power is viewed as an expensive boutique technology espoused by rich liberals like Al Gore who don’t always practice what they preach (remember when his Tennessee mansion turned out to have a huge carbon footprint, even after he wrote such reams on global warming? What were you thinking, Al?) It’s also possible that conservatives haven’t invested as much in renewables and thus don’t stand to profit from increased sales of renewable energy products and systems.

Who knows? When it comes to solar energy, I’d like to think that a chance to save money on energy bills and perhaps even make money as an entrepeneur, would be appealing to advocates of free enterprise. And, the opportunity for America to reduce dependence on foreign oil should appeal to political economists and xenophobes alike. What are we waiting for?