Solar Energy System Engineering
We support solar energy with engineering and consulting services.
For a new project or existing site located on a sunny, unshaded site in Texas, solar energy should always be considered. But wll a solar array work on your particular project and at your site? We can help answer those questions.
Structurally, we can provide an inspection of an existing roof structure to determine if it can properly support the solar equipment while also resisting wind forces on the solar panels. Next, we can create structural drawings for each location showing layouts, orientations and all connection details and parts.
To estimate performance, we can do a simple sun track chart review, or we can provide a full 3D sun study including trees and other shading items using Autodesk Revit.
For larger projects we can also help owners make economic decisions by performing a present value analysis using Solar Advisor Modeling software.
Renovation Solar Array
study renderings by ECO
Structural Engineering for Solar PV Array Installations
Solar PV arrays in high wind areas have many structural issues that should be reviewed, calculated, and certified by an engineer.
We help solar providers and owners make decisions about various mounting systems (direct mount, ballast mount, friction mount, pole mount).
We can develop Revit based structural 3D models like the above to support a designer's concept.
We consider wind loads, component weights, material types and strengths, constructibility, construction sequencing and system durability.
This 'Solar Flower' bracket was designed in 3D by ECO using Autodesk Revit Structure. 
We review the dead loads of solar panels, ballast systems, and mounting racks. Then we look at the wind load on the roof structure based on height and location.
We check loads concentrated on rails, mounting footings, and roof strucural members.
Solar Array structural section detailing by ECO
We look into options for anchoring methods, rack mounting schemes, and best practice roof penetration sealing methods for anchors needed to resist uplift. We calculate wind forces and design structures and the attachment methods to resist those forces.
We review supplier designs and drawings, or create design drawings for permit. We provided on site inspections of the solar array installations with an engineer stamped inspection report certification letter.
Additional Information for Greater Houston Galveston Solar PV Array Installations
As we explain above, ECO provides structural design and inspection services for Solar arrays. ECO is not a solar array provider or an installer and we suggest you leave this up to your selected solar array company. However if you are in Greater Houston and looking for general 'what-if' information to get you started, the following might be helpful.
Orientation - Greater Houston’s Latitude Ranges from 29.7° to 30.1° North
Many 'Google search' guides suggest orienting for the Winter sun if a fixed position is used to optimize annually. But I suspect the text used in these guides was written in the first solar wave of the 70’s focused on northern climates and a need for solar thermal for hot water production. If you need that for Winter hot water production, Houston’s Winter Fixed Optimum is about 55.7 degrees off of horizontal. The same guides list Houston’s Summer Fixed Optimum as very nearly vertical, and Houston’s Spring and Autumn Fixed Optimums as 27.2 degrees off of horizontal.
To get more current results and outputs try one of many free online solar output calculators such as can be found at http://rredc.nrel.gov/solar/calculators/PVWATTS. These can show the optimum monthly and annual output in AC kW-hrs and in dollars per month. They cover both fixed orientation solar arrays and sun tracking arrays.
This online calculator indicates Houston's optimum angle to be at 25° off of horizontal.
However, Houston is also a high wind area so a lower orientation angle may prove to be better. A lower angle 'wind sail' the panels would be much more resistant to wind loads, and the output is not reduced by much, if compared to the 25° optimum angle
Orientation to 20° reduces output by ~0.5%
Orientation to 15° reduces output by ~1.5% (This is close to 3:12 roof pitch)
Orientation to 10° reduces output by ~3.0%
If you really want to recover that 0.5% to 3% loss and more, you can optimize your output by +/-20% by installing a system that allows you to manually adjust the orientation angles four times a year. To do this you would need to climb up and adjust your panel orientation on the first day of each of the four solar seasons:
Winter - Adjust on October 13 (to February 27)
Spring - Adjust on February 27 (to April 20)
Summer - Adjust on April 20 (to August 22)
Autumn - Adjust on August 22 (to October 13)
For a 4kW system, at $0.12/kwh this saves an extra $125 per year (or about $30 per climb!).
If you did not want to climb on your roof, you could do even better if you were to install an automatic full 2 axis solar tracking system. This will adjust the orientation angles in real time of every day to point directly at the sun. You could increase your output anywhere from 30% to 40% over fixed angle arrays. But the added cost is significant.
Is Solar a Money Maker?
We are now approaching a tipping point for price versus return. Right now assuming a reasonable $/kWh, if you finance a system as part of your 30 year mortgage, a new residential solar array can become a money maker.
If you want real numbers, ask your solar array provider needs to do a Present Value calculation with varying predictions for the cost of a kilowatt hour. You can start that calculation with current or predicted Solar array $/watt installed prices. This declining price predicting graph was recently published online by CNET)
Whether you think it is a money maker of not, progressive projects are being constructed with solar arrays, or designed for future solar arrays. (photos from ECO's structural support of a 7kW+ Meridian residential install)
In addition to small and large residential projects, ECO has provided engineering for many commercial installations. These include several high schools, goverment, and private facilities like the Dallas Childrens Museum (below), and the Texas State Aquarium in CorpusiChristi. Retrofit projects require a detailed review of the as-built structures and the structural plans and details before the solar array's structural connection systems can be designed and certified. [Below photo courtesy of APS].
An electric vehicle charging station with solar PV assistance can be engineered by ECO for a high wind area.
