Micro Inverters vs String Inverters

Over the past several years, Micro Inverters have been pushed over the market as something that is the ultimate answer for solar installations.
At American Made Solar and Wind (Mardel Souza Inc), we have refused to make installations with micro inverters for several years for several reasons.
Here is a list of the reasons we try to stay away from Micro Inverters in general:

a)Temperature exposure:
As with all electrical components, microinverters will work better under cooler temperatures. To illustrate this better, you need to look at your laptop or your computer. How many fans and heat elimination devices do you see? Look at the transformer down the street: All the metal and oil are to keep the transformer working under the coolest possible condition.
With this said, the concept of microinverters fails to provide a good point of installation. The recommended point is under the panels, in the rail system. That is in the roof. Even the solar panels experience efficiency loss under higher temperatures. Actually the voltage is lower in a hot summer day in Texas than in a cold day. All electrical components should work better when they approach to absolute zero (kelvin). Even Canada has high temperatures during some months of the year. Life expectancy of such devices is lowered by such temperatures. A full study of this can be seen in this article:
http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0131279

b) Newer panels with high wattage.
As of today, the major companies to buy microinverters only manufactures microinverters for 250watts or lower, which in contrast with the newer panels that are rated 300w>>> the use of older modules is encouraged. Its been our policy to install only newer modules. We try not to keep inventory. Higher wattage in a module means less reails and less labor. Lower cost.

c) Guarantees.
When we install a system, we count on the system to be working for more than 25 years. We have been on business for 11 years and we expect to be in business for much longer than that. By law, all Solar Installations should have a 5 year minimum guarantee. If the life expectancy is yet to bee seen. Although they might be backed up by 10 or higher years of guarantee, I have been on this business long enough to know better. I have seen companies that claim that no microinverter has failed, but companies like Enphase which is publicly own is yet to be profitable. The micro inverters are exposed to the elements. In the coast and some other unfriendly environments, I have seen NEMA4 equipment deteriorate faster than intended. Until I see companies like Enphase making profit, I will continue my skepticism. http://newsroom.enphase.com/releasedetail.cfm?ReleaseID=982485

d)Shades
Microinverters claim that their strong suit is shade and individual control of the solar panels. To a certain extent it is true. However, the new inverters from companies like KACO have different controls over different strings. That means if a string is exposed to shadows or a different roof, the inverter will not allow circular currents and losses from such shades.

Going back to our microinverters, I did call three major suppliers of microinverters and requested information on guarantees and technical data. My impression is that all the big companies are betting on selling microinverters today while they fix all major issues and issue guarantees (if they are claimed) tomorrow. Back in 2012 it was rumored that what some microinverter companies wanted was just to sell the idea to bigger companies like SMA and KACO. Now that SMA and Kaco offer microinverters, I guess the real challenge is to make such companies profitable and their product as good as the string inverters.

I found this article interesting and non-biased, but I think its outdated. String inverters have more control over individual panels this days.
https://www.energysage.com/solar/101/microinverters-power-optimizers-advantages-disadvantages

Alejandro Peña
Mardel Souza Inc
September 16,2016
alexpena@ausasolar.com

Solar Collector issues When disconnected

Its been a while without blogging.  But we are back.

This week a potential customer called us with a very unusual problem.
The family installed a solar water heater from a solar company who is not in business anymore. Sadly this is a common practice we see all over the country, but we generally try to help the person, as means to make the industry in general look better.

Anyway, our techs arrived to the property. The solar water heater was leaking profusely.
It was properly connected. It had sensors and an expansion tank (very unusual as most plumbers do not install it in Texas).  The pressure relief valve was working.

The techs asked if any unusual activity in the house was done. The customer told our techs “We were on vacation and the water company disconnect the water for a bit…”

Disconnecting the water from an open loop solar water heater is like having a fry pan in the stove for days without anything on it, only much more worse.

If the water heater is not fed with continuous water , the system will prevent overheating by expelling the water through the relief valve. Normally, cold water will replace the hot water and the relief valve will close.  If no cold water is available, the heat will increase the pressure inside until it bursts the tank open.

When your installer installs a solar water heater, its convenient to place a sign for the water company to let them know not to disconnect the water from the property, or the water heater will be damaged.

This is the reason we prefer to installed closed loop systems.

I didnt find anything on this issue online, but please post if you find any links on similar problems.

Variable Pitch Product ready.

Over the past year and a half,  we were placed with the task to have variable pitch ground mounted angles for our solar panels.
We have achieved and tested a product that withstands 200mph of windstorm rating.

While solar trackers will still be a better option to follow the sun, they are mostly rated at 80-110 mph being unfit for hurricane ready zones like Miami Dade, South Coast of Texas, Coast of Lousiana , the pacific coast, etc.

Our product will deliver 30% more energy and its not cost prohibitive.
For more information, contact us at:

info@ausasolar.com

956-350-2827

Mardel Souza Inc.

American Made Solar and Wind

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Mid Year Promotion, buy one get the next one 25% off.

It’s that time of the year again. Just like a car dealership, we are getting ready for the new models of solar panels, Inverters and racking for the 2017 season.
The mid year promotion is to promote the movement of inventory of the following sizes:

1500 watts

3000 Watts

5000 Watts

On the purchase of any new powerplant, we are installing the one of this size at 75% the price.  Availability is subject to Final Inventory. We will post once all materials are gone.

Apply for a quote today at:
REQUEST A QUOTE

Basic Math behind solar calculations

Due to today’s tour of several teachers of the University of Texas RGV campus, the following are math terms to remember:

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Pictures taken at Los Fresnos Texas in a 900 Panel Installation. The installation is receiving the 5th year maintenance.

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The inverters are PVPowered 50kw.

Basic Solar Energy Math Concepts

 

The basic unit of power or electricity is Watt. It is actually a measure of rate of energy. Larger units of power are measured in multiples of 1000. For example,

1000 watts     =       1 kilowatt (kW)

1000 kW        =       1 megawatt (MW)

1000 MW       =       1 Gigawatt (GW)

1000 GW       =       1 Terawatt (TW)

If an electrical appliance consumes 1000 watts for one hour, it has consumed 1 kWh of energy or 1 unit of electricity. So, 1000 watt hours = 1 kilowatt hour (kWh). If you run a 100 watt bulb for 10 hours, it again consumes 1 kWh.

Solar panels are characterized by number of watts (Wp) they can produce under Standard Test Conditions (STC) of 1000 W/m2 irradiation, cell temperature of 25 degree Celsius and air mass of 1.5. This is their peak performance. However, the amount of power they actually produce in outdoor conditions depends upon the amount of sunshine.

Air Mass

Air mass is a measure of the distance traveled by sunlight through the Earth’s atmosphere. Since light intensity is attenuated by scattering and absorption, the more distance it passes through the atmosphere, the greater is the attenuation. Consequently, the sun appears less bright at the horizon (morning and late afternoon) than when at the zenith (noon). An air mass of 1 means the sun is looking straight down on the sea surface when it is directly overhead. At any location with latitude greater than 23.5 degrees, the sun is never directly overhead and so air mass will be always greater than 1. The number 1.5 has been agreed upon for the STC (Standard Test Condition) for testing solar panels.

Solar Irradiance and Solar Constant

Solar irradiance is the amount of sunshine incident on a unit area and is typically expressed in watts per square meter (W/m2) or kilowatts per square meter (kW/m2). Irradiance is measured through an instrument called ‘pyranometer,’ which displays the instantaneous power available from the Sun.

Solar constant is the solar irradiance outside the earth’s atmosphere on a 1 square meter surface oriented normal to the sun’s rays. It is about 1367 W/m2. This is attenuated by the atmosphere and the peak solar insolation on a earth’s surface oriented normal to the sun on a clear day is of the order of 1000 W/m2.

This irradiance of 1000 W/m2 corresponds to Standard Testing Conditions (STC) and is called “peak sun” or “1 sun”. If the incident radiation is concentrated 10 times using a lens or a mirror assembly and the incident power increases to 10,000 W/m2, then the irradiance is called “10 Suns.”

Solar Insolation

Insolation is the amount of solar irradiance that is incident on a fixed area over a period of time, and hence is a unit of energy. It is typically expressed in watt-hours per square meter per day (Wh/m2/day) or kilowatt-hours per square meter per day (kWh/m2/day) or even (kWh/m2/year) for a particular location, orientation and tilt of a surface.

Since 1000 W/m2 is “1 sun”, one hour of this ideal irradiance produces 1,000 watt-hours per square meter (1 kWh/m2). This is also known as “1 sun hour.” Colorful maps of solar potential display solar energy in kWh/m2/day, which is equivalent to the number of full sun hours per day. This is a useful parameter for sizing solar panels in the PV systems. More “sun hours” means more potential for solar power.

Global Horizontal Insolation (GHI): It is the solar insolation received by a fixed flat horizontal surface.

Global Tilt Insolation (GTI): The fixed solar panel or collector is generally inclined at an angle roughly equal to the latitude of its location (facing south in India or any place in the northern hemisphere) to maximize the annual insolation received. The insolation received by such an oriented surface is called the Global Tilt Insolation (GTI).

How much energy does one panel produces?

The unit of electrical energy consumed is generally measured in kilowatt-hours (kWh). If an array of solar panels rated at 1000 Wp produce electricity for 1 hour under good sunshine, they have produced 1 kWh or 1 unit of electricity. The total amount of energy they produce during the day is governed by things like solar latitude which is associated with latitude and season, and atmospheric conditions such as cloud coverage, temperature and degree of pollution apart from panel orientation and shading.

For same sunshine, panels produce more power in cooler climates than under hot temperatures. In India, ideal orientation for solar panels is slight tilt towards true south; in South India placing panels flat (horizontal) will also do.

How much space is required to install 1 kW solar panels?

Under clear skies and good sunshine each square meter is receiving about 1000 watts of solar energy. At typical 15% panel efficiency, a 1 sq m area will generate 150 watts of power. For 1 kW power output about 7 sq m area will be required. After leaving some free space, about 10-12 sq m clear roof area will be required.

How much power a 1 kW solar PV system will annually produce in Delhi?

New Delhi has average daily sunshine of 5.5 hours. If we assume loss of 30 days due to rains and clouds every year, then total annual sun hours are 5.5 x 335 = 1843. Ideally 1843 kWh of energy can be produced. But the actual performance will be less than 100 percent because the outdoor conditions are different from standard test conditions of the panels. So, for a 80 percent system performance the annual power production will be 1474 kWh (ie 1843*0.8). In locations where there are shadows and panel tilt is not towards true south, it is often advisable to consider loss of another 10-15%.

How to calculate the annual solar energy output of a photo voltaic system

The global formula to estimate the electricity generated in output of a photo voltaic system is :

          E = A * r * H * PR 

E = Energy (kWh) 
A = Total solar panel Area (m²) 
r = solar panel yield (%) 
H = Annual average solar radiation on tilted panels (shadings not included)
PR = Performance ratio, coefficient for losses (range between 0.5 and 0.9, default value = 0.75)



r is the yield of the solar panel given by the ratio : electrical power (in kWp) of one solar panel divided by the area of one panel.
Example : the solar panel yield of a PV module of 250 Wp with an area of 1.6 m² is 15.6%. 
Be aware that this nominal ratio is given for standard test conditions (STC) : radiation=1000 W/m², cell temperature=25 °C, Wind speed=1 m/s, AM=1.5 The unit of the nominal power of the photovoltaic panel in these conditions is called “Watt-peak” (Wp or kWp=1000 Wp or MWp=1000000 Wp). 

H  is the annual average solar radiation on tilted panels. Between 200 kWh/m².y (Norway) and 2600 kWh/m².y (Saudi Arabia). You can find this global radiation value here : Solar radiation data 
You have to find the global annual irradiation incident on your PV panels with your specific inclination (slope, tilt) and orientation (azimut). 

PR : PR (Performance Ratio) is a very important value to evaluate the quality of a photovoltaic installation because it gives the performance of the installation independently of the orientation, inclination of the panel. It includes all losses.

Example of detailed losses may be

 PR value (depend on the site, the technology, and sizing of the system) : 
– Inverter losses (4% to 10 %) 
– Temperature losses (5% to 18%) 
– DC cables losses (1 to 3 %) 
– AC cables losses (1 to 3 %) 
– Shadings 0 % to 80% !!! (specific to each site) 
– Losses at weak radiation 3% to 7% 
– Losses due to dust, snow… (2%) 

 

All this data

Energy consumption and Demand Measurement.

Today I would like to post about something that is very important to have in place before you even think about setting a solar system.

Lets think about setting a Solar System in Texas. Here at Mardel Souza/ American Made Solar and Wind we have a focus of checking the consumption and Electric Loads before we suggest a system.

If you are located in Texas, and you have an average consumption, your consumption is divided as follows:

60% of your Load goes to Air Conditioning.

17% of your Load goes to your Lighting and Illumination.

23% of your Load goes to Appliances (Refrigerator, computers, etc)

Before thinking about installing a solar system, think about saving electricity.  If you haven’t upgraded:

+Your Air Conditioner

+Your Lights

+All of your appliances are Energy Efficient

DO NOT install a Solar System.  Your Solar Installer should point this out immediately.  We see it all the time. Specially from installers that are not regional (out of state and out of town) who only sell solar systems, they want to install you the biggest solar system possible, without saving on your Loads First.

There is also another factor to consider: What you do not measure, you can not control.

That is, if you don’t know how much KWh  you are using and how you are using them,  consider the following solution: An energy meter that measures constantly how to do this.

See the following graph

monitor

In the graph, we have installed 4 CTs to monitor all the consumptions of a Customer named Cariaga (We keep our customers identity private unless they request not to).

Our customer is using at some time more than 20 KW . His bill is around $520.00 per month. With this tool he now has information on how hes spending the electricity and he can lower his consumption before we install the solar power plant.

A smaller power plant represents a faster Return of Investment.

After doing this, we estimate for this particular customer a 20% savings in electricity which will represent a 20% smaller solar power plant. This is the responsible way to approach a solar installation.

If your solar installer is not doing this, ask them to.

Alejandro Peña

Mardel Souza Inc/ American Made Solar and Wind

956-350-2827

 

 

Educating the community… even our competitors and old suppliers!

This week I came across some very hateful, bigot and racist opinions about our company, our website and some of our employees.

If these comments were from an actual customer, we would take them serious, but the ip address that originates such comments is from Florida and other out of state locations, and the signature is from a Concerned Brownsville Citizen. While we know exactly who made such comments, we are very happy that our competitors and old suppliers are following our blog. This means we at least are educating them in how to proceed in difficult situations and avoid making mistakes with their customers.

The solar industry is an industry that is trying to prove itself to its customers and the general public.

If you buy a television at any retailer, or a computer, or any electrical component, the standard guarantee is one year, which you can extend to 2 to 4 years by paying for additional coverage.

In the solar industry, the minimum guarantee is 5 years by law, and regularly a solar installer or integrator will provide 20 years in the solar panels and 10 years on the inverters.  It is wise to request both the warranties of the factory and the installer and to cover your investment in both ways.
In the past years we have had to back the following manufacturers that went out of business in the United States:

Solyndra

Perlight

Unisolar

just to name a few.

If your installer is suggesting to use microinverters, ask them to give you a non-questions ask guarantee in the United States that is equivalent to a non-micro inverter.
As a general rule, all electric components work beter in cold environments, so I am very skeptic when someone suggest to put an inverter in the warmest enviroment in the property: The Roof.

There are many reviews that cover this topic, just google Micro Inverter Review and aim for the biggest companies with reputable reputation. As we always recommend, aim to American Made product.

Please feel free to email me at:

info@ausasolar.com

Alex Peña

Mardel Souza Inc

956-350-2827

Higher Wattage in solar panels than advertised.

Today we came out across a situation that is becoming more frequent than it should. A solar system produced more amps than its design was intended. This is good news/bad news.  Good news because the customer will get more KWh per day as a result of the overproduction of solar panels. Bad news because the production of more than 60 amps is tripping the electrical protections that the system was originally designed to work under.

Solar panel companies, in a new habit to try to survive (specially American Made or companies that sell in the United States) are giving more output than they advertise. They need to be sure the panels will comply with the advertised output for the next 20 years with the degrading included.

A good advise is to overdesign the electric components more than 30% to prevent tripping protections. If a protection trips more than once, revise the system and change all components after an actual physical reading of the equipment performance.

With several Financing options, why you should go solar today.

There are 4 main reasons to go solar at this moment:

a) Completely reduce or eliminate your energy bills.

With an ongrid system you immediately see the results on the next month’s electric bill. Your system typically reduces 1000kwh per 7000watts of installed equipment.

b)Put your tax dollars to work for you.

Your IRS taxes have to be paid, either by you or by your employer. Why not put those dollars to work for you?
By assigning your tax dollars into a Solar System in your property, you are using the taxes to buy an equipment  to generate electricity for you.

c) Protect against rising energy costs.

Fuel is a hidden tax. We use fuel to generate electricity that we buy from the electric companies. Every fuel increase, increases our utilities. By setting your own solar system, you fix the rates that you will pay for the next 25 years.

d) Increase your property value.

Your property will increase its value, but without increasing the tax payments for it.