Metro Solar Atlanta uses the Solar Pathfinder before all of our solar hot water installations.The Solar Pathfinder operates on a very simple premise. It uses a reflective dome to give a panoramic view of the entire site.

The installer sets up the Solar Pathfinder in the proposed location where the solar collectors will be located, typically on the roof. Declination is accounted for prior to the setup.

A small compass on the pathfinder is used to make sure that the unit is oriented to due south.

Once in position the unit is leveled using a bubble level built into the unit.

Once the unit is in place a digital photograph is taken of the dome. The dome reflects all of the obstructions at the site onto a sunpath diagram.

 The sunpath diagrams are latitude specific and allow you to convert the view on the dome into useful information. The outline of the trees reflected onto the dome reveals where the shading will occur at a specific point in time on the diagram. Deciduous trees that will lose their leaves in the fall or grow them in the spring can also be taken into account. A pen is used to trace the outline of the trees onto the paper diagram, or you can import the digital photo into a computer and use a drawing program to trace the outline.

Here the sunpath diagram is shown without the dome. The diagram represents the path of the sun at different times and during different months.

If you are an  installer  a Solar Path Finder is definitely worth the money at around $200.  If you are a potential solar consumer insist your installer use a Solar Path Finder or other similar device before  any solar installation, whether it’s PV or solar thermal.  They can also be used for landscaping and other similar functions.

]]> http://metrosolinc.com/blog/?feed=rss2&p=148 0 http://metrosolinc.com/blog/?p=135 http://metrosolinc.com/blog/?p=135#comments Sat, 06 Aug 2011 03:17:45 +0000 metroso2 http://metrosolinc.com/blog/?p=135 Metro Solar recently completed another solar hot water installation in Marietta.

This system consisted of one Evosolar collector mounted horizontally with a 30 degree tilt mount to maximize southern exposure.  Here Les & Mike are shown installing the collector.

Attaching mounting hardware to the roof.

Piping the solar loop.

The controller and pump station are shown here. The 65 gallon silver storage tank is shown in the foreground.  This pre-heat system heats the incoming cold water before it reaches the standard gas fired water heater.

(photos courtesy M. Boni)

Simulation software can be used to maximize the efficiency your solar installations before you ever set foot on the roof.

Let’s take a roof orientation of east-southeast or 120°. Let’s say the roof is a typical 5/12 pitch or about 22 degrees. Since the orientation is 60 degrees out from due south we want to model the site to determine the best mounting configuration to maximize our solar exposure.

We ran a simulation on the site using a flat mount orientation to use as our baseline. This configuration returned a 71% solar fraction.

Rotating the collector on its side in a “landscape” orientation would orient the collector to 210°.

(120 + 90 = 210)

This angle goes beyond due south but we can infer that we would have an increased solar fraction verses the flat mount configuration since it is closer to 180°.

Resetting the simulation orientation to 210° and selecting 30° as the tilt angle resulted in a 76.2% solar fraction, or over a 5% increase. A tilt mount rack does not increase the installation cost much so this would be a practical upgrade.

The “book” says that to maximize solar gain during winter to add 15° to the site’s latitude.

(In our case 33° + 15° = 48°)

Running a simulation for every angle between 48 and 30 reveals that the optimal tilt angle for our given orientation of 210° is 35°. This configuration gives us a solar fraction of 76.6% per year. This results in nearly 6% increase in solar fraction per year which means more money saved.

Here at Metro Solar Atlanta we utilize Polysun’s premier simulation software before every solar hot water installation. Many others are available. Simulation software will save valuable time and maximize your installation’s efficiency. Maximizing efficiency is what solar is all about.

Accounting for friction loss in solar loop piping is important to properly size a solar hot water system.  Here at Metro Solar Atlanta we use this engineering principle to correctly size solar hot water systems.

With copper each increase in size also increases the cost. Not only does the piping itself cost more but the insulation costs more as well. So for that reason it makes sense to keep the piping down to the smallest diameter possible and still have enough flow to meet the demand of the system.

Let’s set up a hypothetical solar hot water installation.

Let’s say that the length of the run from the tank to the collector is about 60 feet one way. So that makes the entire loop roughly 120 feet plus the length of the piping through the collector and the heat exchanger. We won’t go into the friction loss of the collector or heat exchanger today, just the piping in the loop since it is usually the major contributor. (residential systems)

In order to figure out the amount of pressure drop due to friction in any pipe you can use the Hazen-Williams equation. The Hazen Williams equation is: Pd = 4.52 x Q^1.85 / (C^1.85 x d^4.865)

where:

Pd = pressure drop

Q = flow in gallons per minute

d = average inside diameter

C = roughness constant (140 for copper)

Let’s start out by sizing for 1/2” pipe. The diameter of Type L 1/2”copper tubing is .545”.

Let’s use a hypothetical flow rate of 3 gpm.

Pd = 4.52 x 3^1.85/(140^1.85 x .545^4.865)

Pd = 8.45psi

This does not include any fittings the collector or the heat exchanger.

This much pressure loss is unacceptable. Friction loss should be kept as low as possible but should not ever exceed 5psi.

So let’s look at the same system using 3/4” piping to see if we can get this number down to a manageable size.

The diameter of Type L 3/4”copper tubing is .785.

Pd = 4.52 x 3^1.85/(140^1.85 x .785^4.865)

Pd = 1.4psi

So the pressure loss is 1.4psi. This number is a lot more manageable. We can live with this even if the fittings, collector and heat exchanger double this number we are still below 4 psi which is below our 5 psi rule of thumb.

Pump curves are labeled by “feet of head” or some other similar title. Pump curves show the relationship between the amount of head the pump can provide at a given flow rate. So we need to convert our pressure loss into feet of head. To do this we multiply the psi by 2.31.

In our example, we would multiply 1.4psi by 2.31 which gives us 3.23 feet of head. After adding in our losses due to fittings, collector and heat exchanger we can use the pump curve to select the proper size pump for our system. This gives us the ability to select a pump that meets our demand and uses the smallest amount of electricity to perform it’s duty.

There are many free online resources that will calculate friction loss for you.

Engineers Toolbox has many online tools.

Under the new law, an expansion of a previous law, businesses are eligible for up to $500,000 in tax credits and homeowners are eligible for up to $10,500 in tax credits to offset the cost of installing solar photovoltaic electricity generating systems. The credits are assessed over four years. When the $5 million ceiling is reached, those eligible taxpayers will be placed on a waiting list and are given priority over taxpayers applying for the credits later, according to a GSEA press release.

There’s no set limit for how much of the credits go to business and how much goes to residential installations, said GSEA Chairman Doug Beebe.

The legislation had bipartisan support, Beebe said. “In Georgia, if you don’t have the Republicans on your side, you’re not going to get anything done,” he said.

To pass the legislation supporters did have to scale it back, according to Beebe. “We wanted $10 million, but we scaled it back to $5 million just based on the response from the governor and legislators.”

Beebe praised the legislation, but said GSEA’s overall goals for the legislative session were not met, according to Beebe. “We had an RPS [i.e., renewable portfolio standard] out there that was shot down,” he said. The group also had promoted failed legislation to incentivize stand-alone solar systems.

The original solar tax credit legislation helped Georgia’s economy by creating jobs. “It has generated jobs, there’s a solar economy that can be grown here.” It supported about 450 direct and indirect jobs in Georgia, Beebe said. Although the tax credit is now doubled in size, Beebe doesn’t expect it to create too many new jobs. “I don’t think it will double the amount of solar jobs. It will allow solar integrators to expand what they already have and maybe hire some more people,” he said.

We recently completed our latest solar hot water installation in Duluth Ga. The system is an EnerWorks type. These systems use a standard water heater as the solar storage tank. The EnerWorks “appliance” mounts to the storage tank and performs the heat exchange and pumping. The controller is also housed within the appliance.

The solar tank is piped in series with the existing water heater so the solar tank “pre-heats” the water coming into the existing tank. This is known as a pre-heat system.

System shown with panel cover removed. Note the heat exchanger, pump and small expansion tank. A supplemental expansion tank (gray tank against wall) was added to the solar loop for added protection against stagnation.

The two collectors are also from EnerWorks. They are 4′ x 8′ glazed flat-plate collectors which do an excellent job of collecting btu’s in southern climates. They are mounted on two C-channels which are secured to the roof with lag bolts. They are connected to the solar tank via 3/8” insulated copper tubing. This solar loop is filled with a 40% mixture of polyethylene glycol and distilled water and is circulated by the pump at the appliance.

The fluid is circulated through the heat exchanger and it’s heat is transferred to the potable water in the solar storage tank. This closed-loop system ensures no glycol enters the potable water, however the glycol is also non-toxic as required by code.

http://www.eia.doe.gov/todayinenergy/detail.cfm?id=390

Since the outbreak of civil unrest in Libya in mid-February, oil and gas production in that country have fallen by an estimated 60 to 90 percent. While Libya accounts for only about 2 percent of global supply, the market impact of such a supply disruption can go beyond volumetric loss. Read more about some of the key factors here. (Article also published in This Week in Petroleum, March 2, 2011.)

Crude volume versus crude quality

Although oil is generally seen as fungible, in fact, crude comes in many different grades of varying qualities and product yields. Libya’s importance to the oil market stems not only from its substantial production, but also from the light, sweet quality of its crude grades. Es Sider, its largest stream, has a slightly lower gravity than benchmark grades Brent and West Texas Intermediate (WTI), (meaning that it is a slightly heavier grade of crude) but a slightly lower sulfur content (meaning that it is sweeter). Another Libyan grade, Sirtica, is lighter than Brent and WTI. Light crudes are, generally speaking, the easiest to process and can be run by relatively “simple” refineries that may not be able to handle heavier or sourer substitutes. A loss of light, sweet crude volumes is, as a rule of thumb, more difficult to deal with than a loss of heavier and sourer ones. This is not only because the refineries that run light, sweet grades have limited feedstock flexibility, but also because most of the spare crude production capacity tends to be at the heavy, sour end of the barrel. Fortunately, current utilization rates for U.S. refineries suggest that there is a significant margin of spare capacity at “complex” refineries that could be used to process heavy, sour crude oil.

Market outlet and destination

Although the majority of Libya’s oil output and most of its natural gas production goes to Europe, its crude market reach is wider, extending all the way to China. But the ultimate impact of any crude disruption goes beyond the immediate buyers of that specific oil. As buyers find substitute supplies for the disrupted oil, those replacement barrels, in turn, are diverted from their original use or destination, causing secondary impacts. Should it be prolonged, a disruption in Libyan exports could have a larger effect on U.S. oil supply sources than the relatively small volumes of Libyan crude actually imported into the United States would suggest. Unlike Libyan production, more than a third of Algeria’s light, sweet crude (a possible substitute from fields relatively close to Libya’s) is shipped to U.S. refiners, which sometimes use it as a blending stock to lighten heavier crude grades. Should those volumes find a stronger market in Europe, U.S. end-users would have to look for alternate supplies. Light, sweet Nigerian crude, which depending on market conditions can wind up in the United States, Europe or Asia, is another case in point. Global crude oil flows will tend to adjust to best match demand needs with available supply sources.

Short haul versus long haul

Location is another important factor affecting the impact of a disruption. The closer the fields where a disruption is occurring are to their market outlet, the more immediate the disruption’s impact on oil inventories and prices is likely to be, unless an alternate supply source equally close to market can be found. In December 2002 and early 2003, a worker strike that curtailed Venezuelan production was immediately felt in the United States, a short-haul destination. Substitute imports from distant Saudi Arabia took weeks to arrive. The rerouting of supplies increased shipping distances, tying up tankers for longer voyages and further tightening a shipping market that had already been firming even before the event. In contrast, while there can be indirect effects on long haul markets from localized substitution, those long haul effects would be comparatively subdued.

Crude versus products

Another way in which a disruption in one market sends ripples through others is via the product markets. Much of the Libyan crude oil refined in Mediterranean refineries is re-exported as product after processing by export-oriented refineries. Italy is Libya’s top crude oil customer, with Libyan crude oil accounting for roughly a quarter of Italy’s total crude imports. But the volume of its refined product exports exceeded that of its Libyan crude imports. Should the disruption force Italian and other refiners to decrease their runs, a sustained disruption in Libyan exports could result in decreased Italian product exports to other markets, tightening product markets well beyond the Mediterranean basin. At this time, however, Italian refinery runs have not been visibly affected by the current disruption.

Market conditions

The impact of a supply disruption is greatly affected by underlying market conditions, such as supply and demand balances, commercial and strategic stock inventory levels, and spare production, transportation and refining capacity. In 1973, the Arab oil embargo had an acute market impact because demand had been growing steeply and the market was already tight even before the event. But in 1967, an earlier Arab oil embargo ended in failure because the market was much more slack. The current disruption is occurring against a context of relatively comfortable spare capacity. Oil inventory levels are generally high by historical standards. But they are not evenly distributed throughout the world and are markedly tighter in Europe, the primary market for Libyan crude, than in North America. The European Brent market had been tightening before the start of unrest. In contrast, spare capacity in both transportation and refining remains abundant, which makes it possible to carry substitute barrels at a relatively low cost over long haul routes and to process barrels of a lesser quality than Libyan crude.

Seasonality

Because demand and supply are both subject to seasonal cycles, the time of year of a supply disruption affects its impact. The current disruption is occurring in a relatively low-demand season. Should it be prolonged, it could conflict with a seasonal ramp up in refinery production ahead of the peak summer driving season. Crude maintenance in the North Sea and elsewhere is also relatively low in the first quarter.

Strategic reserves

Countries with strategic reserves of crude oil and/or petroleum products must decide whether or not to release them in response to a disruption. The decision is a complex one whose potential benefits must be weighed against costs that include a reduction in pressure on suppliers with spare capacity to increase output, and a lower amount of reserves available for use in the future. Most of Europe’s strategic oil reserves are held in products at refinery sites. The United States also holds its strategic reserves in both sweet and sour crudes which can meet a variety of market needs.

Transit corridors

A supply disruption does not necessarily come in the form of a loss at the wellhead, but can result from a transit blockage. Although Egypt is not a large exporting country, it is important to the oil markets as a transit corridor. Earlier this year, as unrest mounted in Egypt, the market grew concerned that oil traffic though the Suez Canal and the SUMED pipeline might be halted. A significant amount of internationally traded oil moves through a number of chokepoints, such as the Strait of Hormuz, the Strait of Aden, the Strait of Gibraltar, the Bosporus and the Malacca Strait, to name a few of the most well known, where it is vulnerable to bottleneck and transit risks. Unrest in Yemen might raise market worries about disruption in the Strait of Aden; although repeated attacks by Somali pirates have already taken a toll on local traffic, oil has continued to flow. In the past, Iran has occasionally raised the threat of retaliating by disrupting tanker traffic in the Persian Gulf if it came under attack. However, even during the Iran-Iraq war, oil continued to flow through Hormuz.

Domino effects

Unrest in one country can raise concerns about potential disruptions in another through a perceived risk of “contagion.” Unrest and upheaval in economies that are non-critical to global oil supply might nevertheless rattle the markets by causing worries that they might spread to neighboring or politically- or culturally-related countries that may be of greater importance to energy market participants.

Market impact

Just as many factors may shape the market impact of a disruption, that impact may manifest itself through a variety of channels. Changes in prompt crude prices are just the most visible and immediate one. Other effects have to do with changes in the relative value of prompt oil supplies across the quality and grade spectrum, changes in the crack spread (the difference between crude prices and product prices) and in the time spreads, or shape of the futures curve. A loss of crude volumes with a high distillate yield will cause distillate prices, not just crude prices, to rise. A supply disruption can cause the price of prompt barrels to rise relative to that of barrels for later delivery – thus pushing the futures curve into backwardation, as opposed to contango (when futures prices are higher further into the future). Cha

A recent story on Yahoo Finance entitled, “Don’t Sweat $3.50 a gallon gasoline” had some interesting statistics, although some not so astute conclusions.

“According to the Energy Department,  growth of motor gasoline consumption stalled out in the middle of the last decade. From a peak of 3.389 billion barrels in 2007, consumption fell in both 2008 and 2009; 2009′s total of 3.283 billion barrels was 3.1 percent below the 2007 total.Consumption has fallen in part because the much-maligned, SUV-heavy U.S. car fleet is getting more fuel efficient with every passing day. For this development, we can thank (or blame) policy, high gas prices, and innovation. The federal standards for mileage of the U.S. auto fleet have been steadily rising, from 26.6 in 2007 to 29.2 in 2010.  Changes in policy and the market have made the fleet more efficient.”

I’d say that thanks would be in order since we are dependent on foreign oil to propel our domestic auto fleet. The rise in popularity of SUV’s in the nineties is in large part what caused the demand to go to the extreme that it went to in 2007. That was a top in consumption. SUV’s are trucks. Trucks get poor gas mileage and at one point were the domain solely of males. When the body styles were modified to suit both genders the amount of trucks on the road doubled and then some. Hence the demand for gasoline skyrocketed. And it seemed that auto manufacturers were in a competition to build the least fuel efficient SUV’s. Suburbans and Yukon’s plumb the depths of fuel inefficiency at 10 mpg each. It’s an issue of weight. For auto manufacturers the incentive to build these vehicles is gone. So I imagine that the 2007 top in consumption will stand for a while, probably forever. But it’s not time to celebrate, for every gallon of demand decrease in the US, China and India make up for in global demand.

The Yahoo article goes on to say, “Remember the 2009 Cash for Clunkers program? The Department of Transportation concluded that “cars purchased under the program are, on average, 19% above the average fuel economy of all new cars currently available, and 59% above the average fuel economy of cars that were traded in.” Yes, sales of pickups and SUVs rebounded smartly in 2010. But today’s larger vehicles are generally more fuel efficient than their predecessors. Meanwhile, every carmaker has ramped up their offerings and sales of fuel-efficient cars, including the Chevrolet Volt, which I drove in November. As these great charts from WSJ.com show, some carmakers that specialize in gas-sippers made big gains in 2010: Nissan and Kia both reported sales gains of 18 percent, while Hyundai saw a 23 percent gain. Hybrid sales, a high-cost path to greater efficiency, are still off their 2007 peak. But there are many more hybrids on the road now. More than 290,000 hybrids were sold in calendar year 2009. In 2010 Toyota alone sold 189,147 hybrids. Meanwhile, the Hummer — like its most famous driver, Arnold Schwarzenegger — has left the public stage.”

Will anyone miss those two? I doubt it.

Here’s more from the article, “Some of the decline is likely due to recession — fewer people driving to work or on vacations, fewer shipments of goods to stores.  But it could also be that the high price of gas and many Americans’ straightened circumstances forced some changes in behavior. When gas prices spiked, people began to carpool, or rode their bikes more, or planned errands more efficiently. And some of these behavioral changes may have stuck, even as gas prices fell in 2009.”

Yeah, I’d say that has something to do with it. With unemployment at 10%, there is definitely fewer cars on the road and I’m not even an economist. People’s behavior has certainly changed. It’s no longer possible to use your house as an ATM to live beyond one’s means. But how did our behavior ever become that way in the first place? Well, it’s the result of a credit bubble that finally blew up with the housing bust. It’s disheartening to hear people lament the fact that Americans have to go back to living within their means as we’ve done for generations. It should be welcomed. We waste too much here.

The article makes some final conclusions, “Of course, we shouldn’t downplay entirely the danger of more-expensive oil. A rapid rise to unprecedented levels of, say, $175 or $200 a barrel would be a painful shock to consumers and to businesses, which would swiftly pass on higher costs to their customers. And context is everything. Should the economy begin to falter, higher gas prices would accelerate the downturn. In a stagnant economy, higher gas prices hit consumers instantly right where it hurts — in the wallet. After all, a huge amount of driving is non-discretionary; most of us have to drive to work and shuttle the kids to and from their activities in our cars. Higher gas prices can thus act as a poorly timed regressive tax. So, yes, a new era of expensive fuel will be an unwelcome development, even as things stand now with the economy. But the ability of our transportation and economic system to weather the increases is much greater in 2011 than it was in 2007 and 2008. The gas pains will hurt, but they won’t be debilitating.”

Wow, what can you add to that prognosis? Let’s take a look at it. “Gas pains will hurt but they won’t be as debilitating.” Hmmm. In 2007 unemployment was below 5%, now it’s over 10%. I’m going to go out on a limb here and say that high gas prices would be more debilitating at this juncture. I don’t think that we would need a rise to $175 or $200 either. I think oil going over $100 will do the trick. $175 would be paralysis.

“The interesting point about this round of M&A activity is the timing. It is occurring at a point when the supply of natural gas is abundant and prices are correspondingly depressed. In fact, natural gas prices remain firmly below pre-economic crisis levels. Much of the reasoning for the price slump can be attributed to prolific gas discoveries in previously inaccessible geological structures, such as Haynesville, Marcellus and Eagle Ford Shale Formations. Couple this with the advent of new technologies to access these unconventional deposits and the result is the surplus of the commodity. According to US Energy Department estimates, the Marcellus Shale alone is thought to hold somewhere in the vicinity of 262 trillion cubic feet of natural gas. This massive geological formation is the largest gas field in the US and touches four states: Pennsylvania, New York, West Virginia and Ohio.”

Large oil companies like Chevron and BP are coming into the domestic natural gas sector right now while gas prices are depressed. These developments are tending to keep a lid on new solar hot water installations because the payoff period for homes with gas water heaters is so long at the moment.  It is our contention however, that these depressed prices are only temporary and they will soon begin to creep back up again in the not so distant future. Lock in your rate (free) now with solar hot water!