Solar Service ,Home Solar Panels
Written by Lisa Walsh

DC Property Owners: Big Hot Water load = Big Solar Incentives

Commercial Solar Service, Annapolis MD

A growing number of building owners, developers and condo associations in the District of Columbia have come to realize that their building happens to be located in the most solar-friendly city in the USA .  Solar contractors, investors and financing vehicles are falling over each other to get solar panels on District roofs and start generating  the lucrative solar renewable energy credits (SRECs).   Whether via Direct Purchase, or $0 solar leases – SRECs are undoubtedly the reason for the solar season in DC (more to follow on those below).

However, before you sign on the dotted line and fill your roof with a 25-year solar PV (electric) system, as offered by 9 out of 10 solar professionals, make sure that you’re not losing the opportunity to vastly increase your return on investment with a Solar Thermal System.

Solar Water Heating Feasibility

The pre-qualification for a Solar Thermal System involves three questions:

  1. Does your building have a substantial, daily (365 day) hot water need? (i.e. apartment building/condos, restaurant, laundry, brewery, health center)
  2. Does your building have a centralized water heating system (as opposed to individual units throughout the building)?
  3. Can the building accommodate additional storage tanks?

If you answered YES to these three questions you really (really) should first consider a Solar Water Heating system either before – or at a minimum – in tandem with, a solar PV system.  (Shopper Beware – unless your solar contact has experience with solar thermal – which many do not – you’re going to have to be prepared to shop further).

What is Solar Water Heating (or Solar Thermal)?

Other than using the sun for energy generation, Solar Water Heating Systems operate entirely differently from their electron-shaking PV counterparts.  These time-tested, technologically mature systems are mechanical in nature and relatively simple.

Moreover, a solar thermal panel is 60 – 70% efficient; whereas a solar PV (electric) panel is typically 17 – 24% efficient.  Therefore, solar thermal panels generate substantially more energy per square foot than PV panels,  monetizing many more SRECs.

Solar Service , Home Solar Panels, Solar Renewable Energy

 

Let’s Review SRECs…

SRECs (Solar Renewable Energy Credits) – along with the 30% Federal Tax Credit and 100% Year 1 depreciation– are what drive the tremendous economic benefits of solar in Washington DC; one of several jurisdictions that have enacted a Renewable Portfolio Standard requiring that a specific percentage of electricity consumed must come from solar.   Whether residential, commercial, or institutional, each time a solar system generates 1 Megawatt hour of energy – the solar system owner generates 1 SREC.  This SREC is then sold via aggregators to an SREC market where it is bought by competitive energy suppliers to allow them to meet their share of the compliance obligation, or else pay a legislated fine (Alternative Compliance Payment, or ACP) for every SREC they are short.  Washington DC currently generates the highest SREC values in the country, largely due to the fact that DC does not have the real estate to install large solar farms which can rapidly oversupply a market and drive down SREC prices.

How much are SRECs Worth?

Washington DC SRECs are currently trading at $395/SREC.  To provide a frame of reference, a 6000 sq ft rooftop in Washington DC outfitted with a 75kW solar PV (electric) system could generate around 90 SRECs/year (over $35,000/year).   Depending on variables such as system size, corporate tax rate and and project site attributes, this SREC income – combined with a 30% Federal Tax Credit and 100% Year 1 depreciation, typically result in IRR’s between 30% – 60% and a Simple payback of 3 – 5 years.    Assuming solar thermal is applicable, this same roof outfitted with a Solar Thermal System could fit a kWh equivalent of a 150kW+ system, generating 180 SRECs/year – and see an IRR of 50 – 80%, with a simple payback in the 1 – 2 year range.

Solar Service ,Home Solar Panels, Residential Solar PanelsMaintenance

Although Solar PV (electric) clients often opt for an O & M (operations and maintenance) contract through their solar installer, Solar PV Systems  have relatively minor maintenance needs; usually an annual inspection along with ongoing monitoring.    Solar thermal (water heating) requires a little more maintenance including a 3 – 5 yearly service which, at a minimum, includes a replacement of the propylene glycol/energy transfer fluid that can degrade with time.  Nonetheless, the impact of service costs on the overall IRR is relatively small and easily absorbed by the increased SREC income.

Written by Lisa Walsh

A Primer on Solar Power

Did you know that attempts to harness the sun’s power through the development of solar cells dates back to the late 1800’s? I am sure that this, and other information, may be new to our readers. This article will provide you with some basic facts about solar power and solar energy. That way, you can join the conversation, and the renewable energy movement!

  • The first successful solar cell was developed in the early 1950s. It was made of silicon, and able to power small electronic devices. This was hailed as the beginning of a new era of energy resources, even then being acknowledged as having the potential to offer a limitless supply of electricity.
  • The first true application of solar cells could be found in the space program at NASA and in Russia. They were the only ones who could afford this technology in the 1960s.
  • The cost of solar cells continued to decline incrementally, but not so significantly that solar was a common source of energy through the 1970s. But, as the 1980s dawned, and ever since, solar power has insinuated itself into all aspects of life, commercially and residentially.
  • The first solar panels for buildings were developed in the early 1970s. In truth, this initial foray into the potential for large scale residential solar power was actually a solar array built into a rooftop. Panel development followed, as the cost and manufacturing efficiency increased.
  • President Jimmy Carter had solar panels placed on the roof of the White House in 1979. Everyone was getting into the act!
  • Welcome to 2018. Today it is common to find solar-powered cars, solar-powered telecommunications, and even solar-powered aircraft. One car company, renowned for their progressiveness, has incorporated solar panels into the roofs of their vehicles!

But, there’s more! Technology continues to expand the horizons of solar energy, making it affordable and applicable in new ways and new places. For example, it is possible that eventually solar panels on rooftops will be replaced with solar shingles!

Or, consider this, a solar fabric is being finalized that can be attached to houses as a cooling device!

We here at Solar Energy Services are excited about the future applications of this renewable source of energy for personal and commercial uses. You can count on us to utilize our superior knowledge and expertise to your advantage. We look forward to serving you!

Home Solar Panels,Eastern Shore MD
Written by Rick Peters

Solar Energy Trends

Some Positive Trends:

Eastern Shore MD,Residential Solar PanelsThe Challenges:

Industry consolidation can be disruptive

Residential solar leasing is fast outpacing cash sales in many of the more developed states, like Maryland. It’s what many Americans want so it will continue to drive the market. It seems to work for more of America.   After all, we do like instant gratification and if I can save $10/month immediately, and feel good about it, where do I sign? While SES is typically strongly advocates for cash sales to our customers who are able, no one can argue the enormous impact and value that the various residential and commercial financing options have delivered. Getting solar access to the mainstream will be the most critical piece to advancing the development of distributed solar. It really has been transformational so far.

There’s other good news. System Pricing, though leveling off somewhat, has dropped dramatically in the past 5 years. While incentives decline as planned, the industry continues to drive down installation costs to maintain the impressive paybacks and internal rates of return.

Beneficiaries of solar price reductions include states like Maryland, who had the foresight to seed this industry over the last 6 years. Government and industry partnership in Maryland has built an economic environment that supports solar development and as a result, it is sustaining 2200 jobs while Maryland continues to meet its solar RPS goals. That’s right, our industry delivers over 2200 paychecks in Maryland. In fact, there is now a solar thermal equipment manufacturer in Baltimore. Much to be pleased about.

There’s also a darker side. Bankruptcies and consolidation of solar companies have carried the headlines quite a bit in the last year especially. While a natural part of the tech/business evolution cycle, consolidation and shake out are always disruptive, not only to industry members, but also to consumers of these solar energy products and services. As a result, all of the solar “investors” are asking lots more good questions – particularly about the longevity of the manufacturer and the installer. Popular questions, particularly in the solar PV panel world, are “Who will be here to support my warranty?” and “What is the design track record of these systems?”

The beneficiaries of these trends will be those with a proven commitment to the industry either through time or capital. It’s that commitment that gives customers confidence of future support if and when it is needed. Whether it’s an installer with 35 years experience or a manufacturer like SunPower that has 25 years in business, longevity is a key indicator of future availability to support the install base.

Commercial Solar Energy ,Residential Solar Panels
Written by Lisa Walsh

Inverters: One Size Does NOT Fit All

Home Solar Panels ,Washington DC Solar,Commercial Solar Energy, Residential Solar PanelsIf you own or are planning to own your own solar power system, you’ve probably heard of an Inverter.    Although a vital part of any solar electric system, inverter choices can easily be overlooked in the shadow of seemingly more important decisions such as installer and solar panel options.   I mean, doesn’t an inverter just change the solar energy (DC) to house energy (AC)?  How complicated can it be?  Contrary to what your salesman or inverter manufacturers may have you believe, there is no “one size fits all” inverter.   As with many electronic devices; design, cost, warranty, time-testedness and monitoring capabilities are variables designed to offer as many choices as the different homes, businesses and climates they inhabit.  For example, you wouldn’t want to pay a premium for an inverter designed to deal with partial shading issues – if you have zero shading.  At a minimum, you’d at least appreciate knowing how the “other” inverter would affect the contract price.  So, in this spirit – let’s take a preliminary tour of the Inverter (or optional, microinverters).  Inverters have three primary functions:

  1. Inversion of the incoming DC energy (direct current) into home and appliance-friendly compatible AC energy (alternating current).  This is its main function.
  2. An MPPT (maximum power point tracking) function ensures that the inverter receives the maximum amount of power from the solar panel by adjusting the voltage (load) to match what the inverter wants; managing the complex relationship between sunlight and other varying conditions.
  3. Various electronic monitoring sensors that will, for example, detect when there is a fault in the grid-tied solar panel or on the grid and shut down power so the solar system cannot injure power-line workers during a grid outage.

The most traditional form of Inverter is a String Inverter, so-called because it is connected to a line or “string” of solar PV panels.  One solar power system, depending on the size/number of strings in the system, may have one or several string inverters which sit in parallel and convert the arriving DC current into an AC output.

Commercial Solar Energy, Residential Solar PanelsThese six string inverters service a large commercial solar electric (PV) system. Each inverter services forty solar panels, on four strings of 10 for a total of 240 panels.

Micro-inverters and Power Optimizers

Another type of inverter is the Micro-Inverter.  As the name suggests, this inverter is a smaller version of a string inverter, but rated to handle the output of each individual panel.  Therefore an inverter is located on the back of every solar panel unlike a string inverter that is often located on the side of the building/ground level.  Micro-inverters have been around almost as long as string inverters.  Historically, the manufacturing costs involved with making a dozen “mini” inverters couldn’t compare to the cost of one large string inverter.  However, as the solar industry has grown  – so has the demand for the micro-inverter; driving up demand while reducing production and distribution costs.

In response to the popularity of the micro inverter, Tigo, followed by String inverter giants SMA, developed a device called the Power Optimizer that works in conjunction with a string inverter.  As with micro-inverters, power optimizers are placed on the back of each panel and provide an MPPT function to each panel – limiting individual shading and orientation effects to the panel they’re attached to as opposed to the whole string.  However, because they are designed to operate alongside a string inverter they do not require individual transformers and are therefore much smaller, lighter and most importantly, cheaper than micro-inverters.

Solar design expert, Rich Schroeher says there is a time and a place for all three of these inverters:

Q:  Aren’t micro inverters better when the solar arrays are facing different directions or have different roof pitches?

Rich:  With micro-inverters, in essence, each solar panel is it’s own solar system, independent of the other panel/ inverter combinations, so various orientations of panels are easily accomodated.

With string inverters, a different inverter must be used for an array that is facing a different direction, or at a different pitch than the other arrays.

One way around this is string inverters that contain 2 MPPT inputs. These are, essentially, 2 inverters in one. They also have the added benefit of being able to handle more of the array than their rating. For example, let’s say you have two arrays facing different directions: one South facing and one East facing.  The entire system would use a 5000 watt inverter divided into two channels of 4000 watts for a total of 8000 watts.  The inverter will still only supply 5000 watts but when the south roof starts getting sun, the east roof is losing it. If at anytime more than 5000watts is being fed to the inverter, it just limits it to 5K.

 

Q:  Some homes have partial shading on the roof. How do you know when to use a string inverter – possibly with dual MPPT, or a power optimizer – or stick with a microinverters that will ensure a shaded panel won’t negatively affect the whole array’s output?

Rich:  It depends on the situation. Microinverters and optimizers can help with small areas of shading but are not a cure-all. They work best for an application where a small % of the roof is shaded at various times during the day, such as a chimney shading a few collectors where the shadow moves during the day.

Q:  Are there any longevity differences between string and micro inverters?

Rich: Opinions vary.  A solar system with 24 micro inverters, as opposed to 1 string inverter, has 23 more points of failure.  Plus the extreme temperatures that microinverters are subjected to can be an issue; electronics generally don’t like heat.  Microinverters are also located on the roof behind each panel, as opposed to the string inverter which is usually conveniently located close to the main electrical supply on the ground level.

Q:   Enphase microinverters claim to get greater efficiency, up to 16%, than their string counterparts due to the fact that the maximum power point is matched to the solar panel as opposed to the inverter, which limits the available output.

Rich:  In a Partial shading situation this could be true. If there is no shading at all or very early or late in the day when production is very low anyway it wouldn’t be near that high.

There are only two notable benefits that microinverters offer in a zero shade situation: they eliminate the string inverter losses from module mismatch (very small differences between modules), around 2 – 3%.  They also help with DC wiring losses.  Combined those two losses may be 5% overall.  This all assumes that the module attached is not too large (powerful) as to have any appreciable amount of clipping – meaning the full power of the module is limited by the inverter.

Q:  Microinverters, are more expensive than string inverters, at $.70/watt with a twenty-five year warranty.  Although String inverters are as much as 50% less, they often come with only a ten year warranty.  Doesn’t the microinverter’s longer warranty cover the inflated cost?

Rich:  In the long run probably no. Most string inverter companies’ offer extended warranties up to 20 years. Some include the cost of labor to replace. The labor cost to replace is about equal for a string inverter and a microinverter or perhaps a bit lower for string inverters depending on where in the array a failed micro is located. Say you have a system with 20 panels and the labor cost for inverter replacement is $150.00

      String inverter cost over lifetime $150.00

      Microinverter cost over lifetime  as much as $3,000.00 Plus 19 more scheduled trips and possible inconvenience to the owner. 

Q:  SMA’s new inverters include a “Secure Power Supply” capability.  What is this?

Rich:  This is a small (15amp) receptacle that is powered up when the grid goes down. As long as the sun is shining it will provide 120 volts of AC electricity. My first thought was to power a refrigerator or freezer to help carry a system owner through the outage without food spoiling.  It can’t be used at night but it will let you use some of the system during outages.

As is often the case, there are no cut and dry answers here. Variables such as system size, shading, orientation, panel layout and budget will determine whether a String, MPPT optimizer or micro-inverter may or may not be the best choice for your roof.  Most installers/designers worth their salt will consider all of these options and come up with the best solution for your house.

Written by George Young

Offset Your Oil-Guzzling Water Heater with Solar!

Offset Those Oil-Fired Water Heaters with SOLAR

Why oil-fired water heaters?  In many parts of the country there are no local gas lines for residential distribution.   In the Chesapeake Bay region where we operate, this issue is very common in the many river communities that are close to our world famous estuary.  The reason for this is primarily because there are so many peninsulas that don’t offer the high density to justify pipeline expenses.  In these areas, customers are forced to use other fuels like electricity, propane, and oil to heat their homes and domestic hot water.  This article will focus on the oil-fired boilers that are common in this region as well as in the Northeast US.

Cost of Gas Alternatives:  Many homes have heating boilers that run on fuel oil.  These boilers have tremendous heating power and can recover loads quickly.  They also tend to be relatively inefficient, dirty, and expensive to run.  Many of these boilers also have an on-demand water heating feature that adequately satisfies the household’s water heating load without the need for a standby tank.  This all sounds great except the price of home heating oil continues to climb with recent prices around $4/gallon on in our area.  To put that in perspective, the equivalent price for natural gas on an energy density basis would be about $1.00/gallon.  When oil users are paying 4 times the rate of those who have access to natural gas, they can hardly afford to be wasteful in how they operate their boilers.

Summertime Blues:  Here’s the dirty little secret about that on-demand oil-fired water heater on your boiler.  It is typically programmed to keep that big hunk of metal hot, all summer, waiting for you to call for hot water.  So a premium for your oil (compared to gas) is not the only thing you are paying for.  During summertime your air conditioner is competing with your heat-radiating oil-fired water heater.   So, here’s the way I – a not-so-proud owner of an oil heater – circumnavigated this issue:

My Solution:  I have solar photovoltaic (PV) on my home, but when I got into the solar business in 2008 the first thing I did was deploy solar water heating in my family’s home which allowed me to shut down our boiler for about half the year.  We also did some other control modifications for efficiency.  The first simple control is used to automatically reduce the boiler target temperature as the outside air temperature increases – for example, you don’t need 180 degree water to heat the house when its only 50 degrees outside.  Secondly, we converted the boiler to “cold start”, so it no longer wastefully heats on standby when we have a big tank of solar-heated water waiting to be used.  My family’s solar thermal system is slightly oversized (there are 3 forty square foot panels instead of 2) so that it could be integrated with our hydronic space heating system to give us a little space heating help from the sun.  [See our recent blog on combi-systems (hyperlink)].

So that’s the good news.  The GREAT news is that there has been absolutely no convenience impact on how we use hot water or space heating.  The system has saved us about $800/year in oil       expenses, the majority from offsetting our inefficient water heating, and the remainder from space heating.

Furthermore, the solar heating system is optimized in the summertime, all-but-negating the use of the oil-fired water heater.  The air conditioner has to work far less without having that heat-radiating boiler inside the home – like most are.

People are learning that different homes and circumstances often can benefit substantially more than others when you consider various renewable or energy efficiency technologies.  Oil fired water heaters are some of the sweetest low hanging fruit in solar.  In fact, I joke with my residential oil supplier that we should team up so he can get out in front of this trend that is eating into his oil sales.  He said, “no thanks – I’ll ride this as long as I can”.

If you forgot to make a new year’s resolution this year and you heat your home and your water with oil, then plant your flag!  If you’ve got some solar exposure, you must commit to get a free solar thermal assessment in 2014 and stop pouring money and finite resources down the drain.

Written by Lisa Walsh

Supercharge your Solar Water Heater

Solar Thermal not Solar PV: When talking about solar and space heating, it’s worth mentioning that the panels used for this type of solar application are not the same panels that power a house, a light, or any other electrically powered appliance. In fact, the only similarity between a PV (photovoltaic/electric) solar panel and a Thermal Solar Panel is that they both absorb solar energy. However, how each panels processes and distributes that energy is entirely different.

Enlarged Domestic Hot Water System: In order to make a solar space heating system cost-effective, most space heating systems are designed to include the home’s domestic hot water supply – thereby offsetting the gas/oil/electric bill and returning the solar system’s investment. Therefore, any space heating system is basically an enlarged solar water heating system. These systems that combine solar water heating and space heating are often referred to as combisystems. This combination is achieved with a solar storage tank that comes equipped with two separate heat exchangers; one for the domestic hot water loop and one for the space heating loop. The cooler water returning from the heating system passes through the upper heat exchanger on it’s way back to the boiler where it does one of two things: It picks up some heat that was generated by the solar system or, if the tank is cooler than the returning water, acts as a buffer tank allowing the boiler to have fewer on / off cycles thereby making it more efficient.

Space Heating Infrastructure: Radiant floor heating systems are highly compatible with solar thermal energy. This is mainly because these systems are designed to operate at low temperatures and thus the solar system can contribute energy more of the time. Hot water baseboards, radiators and other hydronic heaters can also benefit, especially if an outdoor reset control is installed. The outdoor reset control adjusts the boiler’s target temperature according to the outdoor temperature.
Forced air systems can also be modified to accommodate solar by placing a fan coil inside the existing duct work. A controller senses when the fan needs to be activated and, again, a conventional back up system kicks on as needed.

Heat Dissipation in the Summer: Of course here in Maryland/Washington DC,  in our Mid-Atlantic climate, solar energy for space heating is being summoned at a time of year when insolation (sunshine) levels are much lower than the rest of the year. Therefore more solar panels are required to meet the quota. A family of four would realistically need two, 4′ x 8′ flat plate collectors for their home’s hot water supply. Depending on the required space heating square footage, this collector size may be increased anywhere between 30 – 100%. To avoid overheating in the summertime when space heating is no longer required, there needs to be a mechanism to dispose of the excess heat. This can usually be achieved with anti-stagnation functions on the controller or by installing a heat dissipater on the roof. An ideal situation is to redirect this excess heat to a pool or hot tub, thereby creating a year round triple-application system that provides the largest return on investment.

Maryland Solar Company ,Commercial Solar Energy
Written by Lisa Walsh

Maryland Solar Pool Heaters – Top 10 FAQ’s

  1. Maryland Solar Company, Commercial Solar EnergyWhy Heat My Pool?
    Private swimming pools are a significant investment. As with any investment, it’s all about payback. A fully sized solar pool heater can raise the pool temperature 10 – 15 degrees, so many of our solar pool heating customers are able to swim from May until October – doubling their swim season, and doubling the payback on their swimming pool investment.
  2. How does a Solar Pool Heater work?
    Pool heating is the most fundamental use of solar energy. Much like when water is warmed in a garden hose, thin plastic solar pool collectors are custom-fitted to a nearby sunny roof. Automatically controlled pool water is pumped, using your existing pool pump, through the pool collectors and the heated water returns to the pool.
  3. How much does a Solar Pool Heater cost?
    A site visit (provided at no cost) is needed to provide an accurate cost proposal, as all pools, roofs and solar exposure levels are different. However, based on experience – most systems have an installation cost of $13 – $16 per square foot of collector area. This area size is equal to at least HALF of the surface area of the pool. (i.e. a 18’ x 36’ pool has a surface area of 648’ sq. ft. Therefore the homeowner would need at least 324 sq. ft of solar pool collectors).
  4. How does the cost of buying a solar pool heater compare with heat pumps?
    The upfront cost of installing a solar pool heater is much the same as installing a heat pump. However, with a heat pump the homeowner will continue to have elevated utility bills, whereas solar energy is free.
  5. Can community pools be solar-heated?
    Yes. The main requirement is a large enough nearby roof to house the solar collectors. Collectors can also be ground mounted if the facility has a large enough, unused ground area nearby.
  6. Can the solar collectors also be used to heat my home’s water tank?
    No. The solar collectors used for i) domestic water heating and   ii) solar electric are entirely different both from each other, as well as pool heating collectors. SES installs all three types of solar energy and can provide proposals for each.
  7. What about maintenance? Do I have to hire anyone to open or close the pool heater?
    Solar pool heaters require no regular maintenance. They are simply opened and closed with your pool at the beginning and end of each season. The panels drain automatically.
  8. Will the solar collectors hurt my roof?
    No. In fact, the collectors are made from a strong polymer compound that actually serves to protect your roof from the elements.
  9. How long can I expect my solar pool heater to last?
    We use Solar Industries (Aquatherm) pool collectors which were tested and survived a grueling 23 year life expectancy test performed in the Arizona desert.   In addition, Solar Industries offers the strongest warranty in the industry.
  10. How long does the installation take?
    Most installations take a single day, but sometimes two.
Residential Solar Panels, Solar Service
Written by George Young

Environment Showcase at the Annapolis Film Festival 2013

Residential Solar, Panels Solar ServiceSave the Date: March 23rd, 9.30am at St. Johns College (Francis Scott Key Auditorium)

In February 2012, a few of us local, environmentally-minded companies got together and welcomed ex-CIA director James Woolsey, among others, to lead a panel discussion after the showing of Energy On Trial. The event was a great success

– just what you’d want from at this type of event – a few hundred local folks showed up, we watched a thought-provoking movie and either participated or bore witness to the controversial banter back and forth between panel members (nuclear vs other renewables).  As folks tumbled out into the lobby of the Auditorium they were met with some yummy treats and a few of us local, sustainable organizations and businesses ready to mobilize their renewed commitment to the environment.

This year, we’ve joined the larger platform of the Annapolis Film Festival and incorporated an Environmental Showcase at St. John Francis Scott Key Auditorium that features Robert Redford’s film “Watershed”, an environmental panel discussion as well as sustainable company/organization presence and refreshments.  Non-for-profits such as Chesapeake Bay Foundation and Annapolis Green will be alongside locally owned businesses such as Solar Energy Services, Inc. and Rain Barrels of Annapolis.

Download the Environment Focus flyer

Purchase tickets and passes here.

The Environment Showcase is part of the larger Annapolis Film Festival, March 21-24, 2013. In partnership with the City of Annapolis and the local Arts and Business Communities, the Annapolis Films festival aspires to bring a major new cultural event to our area.  90 films in four days will be showed at various sites around Annapolis involving guest speakers, filmmakers, parties, and much community involvement.  For more information contact The Annapolis Film Festival

Written by Lisa Walsh

Solar Monitoring

Homeowners can see how their daily sunshine dollar is spent

Most homeowners who have invested a tidy 20 – 30K in a whole-house solar electric system want some idea of exactly how much, and when, their solar system is generating energy. This is true especially given the fact that most solar systems in Maryland, DC, Virginia and surrounding area are grid-tied. The solar electric system provides a large portion, though generally not ALL of a home’s electricity, with the balance coming from the traditional energy provider (BGE, PEPCO, etc.) during periods of high usage and/or low sunshine levels. So most customers still receive an electric bill, albeit greatly reduced. An online solar monitoring system keeps the homeowner plugged in to how much energy they are receiving from the sun versus their utility “back-up”.

The monitoring system is tied to the Inverter… (An inverter, by the way, converts DC power to usable AC power.)

SES often uses Enphase Microinverters in residential solar electric systems. This is our preferred monitoring system for a variety of reasons, including simplicity, cost-effectiveness, and customer support. With this system, each panel has its own inverter and associated monitoring. In contrast, solar systems that use only one inverter for the whole array do not have the ability to monitor performance of individual panels; just the entire as a whole. Microinverters, convert, quantify, and record the DC to AC energy conversion on each individual panel, independent of the other panels. These microinverters come with the Envoy Enlighten monitoring system. The homeowner simply clicks on a link from on their computer or Smartphone to see live readout of their current system power generation along with a robust record of historical data. Both the homeowner and system installer are notified when Enphase detects issues such as a panel or inverter failure (a rare occurrence), communication issues or shading (due to tree growth etc.), enabling a speedy remediation. Fortunately, true solar panel/inverter issues are few and far between, if at all, keeping the monitoring system employed at its optimum job: counting the rays of sunshine that power your home.

Commercial Solar Service ,Annapolis MD
Written by George Young

On-Demand as Back-up for Solar Water Heating?

Solar veteran Roger Perry gives his two penneth about on-demand water heaters as viable solar water heating back-up candidates.

CAN I — USE AN ON-DEMAND HEATER AS SOLAR BACK-UP?

Commercial Solar Service ,Annapolis MDAll solar water heaters in Maryland, D.C., and the Mid-Atlantic provide a family of four with around 75% of their annual hot water load. Most customers use their existing electric or gas sources for the remaining 25% backup (usually needed dead winter.) On-demand water heaters have a couple of advantages over tank-type heaters, but they are somewhat mitigated with a solar system.

The touted advantages of on-demand heaters:

Endless hot water– In a solar system with a properly sized back-up you will, pretty much, have endless hot water in the summer and plenty of hot water the rest of the time.

Large savings because of no stand-by losses– The claims of “up to 40% savings” are a bit exaggerated in all but the oldest water heaters. Our solar tanks are extremely well insulated and their stand-by losses are minimal. Also, in a solar water heater, the tank is an integral part of the system so the small stand-by losses are a fact of life.

Then there are the disadvantages with on-demand heaters:

On-demand heaters can get very confused when fed water that is already hot– This can result in temperature fluctuations as the heater tries to adjust or, in extreme cases, the heater shutting down on high limit.  One way we have gotten around this is to use a motorized 3-way valve that bypasses the on-demand heater.  This works well but adds to the complexity of an alredy complex piece of equipment, which leads me to…

They are very complex pieces of equipment– A standard water heater, gas or electric, has a bimetallic spring that moves to make an electrical connection when it cools, and moves to break that connection when it heats up. It doesn’t get a lot simpler than that. An on-demand heater must sense the flow of water (demand), measure the outgoing water temperature, and adjust the amount of gas to feed the burners so as to maintain a constant temperature at the tap. It also has to do this very quickly so as to not deliver water that is too cold when another tap is turned on or too hot when another tap is turned off. After a couple of years, scale begins to build up in the water valve; the unit needs to be descaled or it will stop working. For safety reasons, the default for most problems in any of these systems is for the unit to shut down.

All of this said, believe it or not, I do like these systems and would recommend one to anyone who could not get a solar system for some reason. I just don’t think they are worth the added headaches as a back-up for a solar water heating system.

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