Static vs tracking solar ground mount systems

Wednesday, September 29, 2021
Training
by
Veli Markovic

Solar tracking systems produce more energy but.  .  .  .  .

Most of us are aware that solar tracking systems produce more energy per kW of solar installed but the question often asked is this a more viable option than a static system?

In this presentation we will look at the different tracking systems from a large ground mount system perspective, how much increased production wise over static systems, cost of systems, cost of maintenance, and other factors.

Solar trackers

A solar tracking system maximizes production by orienting the panels to follow the sun during the day. 

Solar trackers are typically used for ground-mounted solar panels and tend not to be used in domestic situations.

The angle at which the sun’s rays hit the solar panel (known as the “angle of incidence”) determines how well the panel can convert the incoming light into electricity and the narrower the angle of incidence, the more energy a photovoltaic panel can potentially produce. 

Solar trackers orient panels so that the solar resource strikes them perpendicular to their surface.

Solar trackers: single versus dual axis

A single-axis tracker moves your panels on one axis of movement. These configurations allow your panels to arc from east to west and track the sun as it rises and sets.

A dual-axis tracker allows your panels to move on two axes, aligned both north-south and an east-west. It can track seasonal variations in the height of the sun in addition to normal daily motion.

Active vs. passive solar trackers

Most tracking systems out there are active which means that the tracking system is motor driven, to energise a mechanical device that tilts the attached solar panels the right way. 

Passive solar trackers also track the solar rays but they move by using the heat from the sun to warm a gas which expands causing a mechanical movement of the solar panels. When the sun moves and the gas cools, it compresses again and the panels move back.


How much extra output do you actually get?

Generally, a solar panel system with a single-axis solar tracker installed sees a performance gain of anywhere between 10 to 30 percent and in the right situation, a dual axis tracker can produce up to 40% more than a static array.

But at what cost? Systems that incorporate a tracking configuration:

  • Tend to cost more per watt ( or do they)
  • Take up more room, land costs
  • More things to go wrong, Murphy’s law

When analysing the cost effectiveness of any particular system will need the appropriate tools and assumptions have to be made.

The Assumptions: Static system firstly

So we are talking ground mount systems here, off course, and some of the assumptions are as follows:

  • System size is 1.28MW
  • Location is Melbourne, Australia, 37.8136° S, 144.9631° E
  • Static system panel tilt at 25.5 degrees North ( Equator) facing
  • Average output per kW installed is 3.6 kWh


The Assumptions: Static system secondly

Some more assumptions:

  • Electricity price increases 2% every year
  • Panels degrade at 2% in the first year and 0.25 % every year after that
  • Maintenance for the static system is $1000 in the first year increasing 2% every year after that
  • Cost per watt supplied and installed for the static system is $1, 1.28 MW system is $1,280,000
  • Occupies a little under 1.4 hectares

Static systems: the results

A 1.28 MW system @25.5 degrees North facing in Melbourne Australia will produce:

  • 4,612.01 kWh/day
  • Price for electricity is $0.25/kWh, export is $0.07/kWh
  • 50% of solar produced service the load, 50% goes to the grid
  • Savings first year, $268,341.58
  • Savings after 10 years, $2,803,595.17
  • Savings after 25 years, $7,787,510.68


Static systems: the results in table form


The Assumptions: Single axis tracker

So a lot of the assumptions are the same as the static system but some aren’t:

  • Sill in Melbourne and electricity price still increases 2% every year
  • Panels degrade at 2% in the first year and 0.25 % every year after that

Now let’s assume that the increase over a static system is 25% and:

  • Panels tilt max 50 degrees East and West
  • Average output per kW installed is now 3.6 + (3.6 x 0.25) which is 4.5kWh
  • Maintenance for the tracking system is $1250 in the first year increasing 2% every year after that
  • Cost per watt supplied and installed for the static system is $1.20 , 1.28 MW system is $1,536,000
  • Occupies 20% more than the static array so looking at least 1.68 hectares

Single tracker systems: the results

A 1.28 MW system with East West tracking:

  • 5,783.71 kWh/day
  • Price for electricity is $0.25/kWh, export is $0.07/kWh
  • 50% of solar produced service the load, 50% goes to the grid
  • Savings first year, $336,768.90
  • Savings after 10 years, $3,518,641.71
  • Savings after 25 years, $9,774,096.76


Static systems: the results in table form

Static versus Single tracker comparison: investment

Post Mortem

So the tracker system is the more economically feasible based on the assumptions made.  We have assumed a price to install of $1.20/watt and one question to ask is at what price does the static system become more attractive?

I have used goal seek, part of the What If analysis in Excel and the answer to that question is:

 a little over $1.25/watt 

Also that question can be asked in reverse. How much does the $/watt price have to drop before the static system becomes more viable than the tracker system?

The answer is $0.95/watt.    Both calculations were based on the IRR for a 10 year investment.


Let’s go a little further

I have assumed a % increase over the static system of 25% but what if we use, for example, another lower %?

Let’s assume a 20% increase.

How does this affect our overall single tracker performance?

Let’s now assume a 10% increase.

How does this affect our overall single tracker performance?

Other factors to consider

For all examples given I have assumed a 50:50 split in regards to negating draw from and export to the grid. Now with a tracking system the output curve tends to be a lot flatter which in a lot of cases more closely matches the consumption load profile of a lot of sites. 

So what happens when the split goes to 70:30 in favour of direct consumption?

All the results: 25 year savings


Conclusion

When comparing to ascertain what is the best system, static versus tracking many assumptions need to be made in addition to the reality of actual energy production and how it matches with site loads etc.

The reality is that a tracking system of the same capacity compared to a static configuration will produce more energy at any point in time but at what cost? I have given examples ranging from $0.95/watt to $1.25/watt.  When talking of IRR in these examples I have selected 10 years but if another figure was selected this would alter these results. 

In addition if the cost of the land was factored into the calculations, the results would be different again.

If you’d like to see what Greenwood Solutions get up to in the real world of renewable energy, solar, battery storage and grid protection check out our industry and commercial pages:

https://www.greenwoodsolutions.com.au/industry 

https://www.greenwoodsolutions.com.au/commercial

https://www.greenwoodsolutions.com.au/news

https://www.greenwoodsolutions.com.au/commercial/customer-stories


About the author

Veli Markovic

CEC Designer
Veli has nearly two decades of experience in the renewable industry. He is passionate about providing people with valuable education and is highly regarded throughout the industry as an educator and operator.
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