A utility-scale solar PV park needs flat, unshaded land with at least 1.6 m of topsoil, a short route to a grid connection point, good road access and no flood risk. As a rule of thumb each megawatt takes about 2 hectares, although large sites can approach 1.5 hectares per MW. These were the starting points in an outline proposal for a 30 MW solar park in a South-East Asian special economic zone.

The challenge: a large load and no confirmed site

An economic zone had issued a request for proposals for its power development plan. The proposal set out to answer a basic question before any equipment was ordered: can 30 MW of solar generation actually be built and connected there? That depends on land, grid and sunshine, in that order.

The assessed solar resource was at least 1,600 hours of useful irradiation a year. For 30 MW, that is a gross potential of about 48,000 MWh a year. The proposal assumed an initial load factor of 60%, rising to 80% in later years, so the real figure depends on how the plant is dispatched and how the grid takes it.

The approach: build in modules, check the site first

Modular build-out

A PV plant is modular, so size does not add much complexity. The proposal gave a planning figure of about four weeks and a crew of no more than 20 workers to install one megawatt. The target was to install the 30 MW in 5 MW batches over three years, at a pace of 5 MW every six months. Smaller batches let the investor and the grid operator confirm that each stage works before the next is built.

The components

A PV system has four main hardware elements, regardless of whether it is grid-tied or off-grid:

• Racking made from galvanised steel and aluminium.
• PV panels. A typical panel has 60 polycrystalline cells and a nominal output of about 250 W.
• Inverters that convert DC to AC.
• A step-up transformer to match the voltage at the grid entry point.

A panel’s efficiency decides its area for a given output. An 8% efficient 250 W panel is twice the area of a 16% efficient one. Output also falls over time, by around 0.5% a year for a typical panel, and manufacturers commonly guarantee about 90% of rated output at 10 years and 80% at 25 years. The business case should allow for that decline.

The site checklist

The proposal listed nine value drivers for choosing a parcel of land:

1. High solar resource.
2. No shading from mountains, trees or buildings.
3. Easy access to a grid connection point.
4. A flat or evenly sloping site, such as farmland.
5. Topsoil at least 1.6 m deep before bedrock, which allows helical steel screw foundations that need neither concrete nor pre-drilling.
6. Good access for heavy transport.
7. Land that is inexpensive to secure.
8. Freedom from environmentally sensitive flora and fauna.
9. Freedom from flooding.

Distance to the grid is the variable that is easiest to control. AC cable is costly over long distances, so the shorter the run between the plant and the connection point, the lower the installation cost.

Layout

A typical 1 MW layout stacks panels three rows high, each row just over 3 m tall, which needs about 15,000 m² per MW. The planning figure of 1.5 to 2 hectares per MW is higher than that, because the site also needs space for offices, workshops and the grid connection facilities.

Why a staged route to development works

Before committing, the proposal set out a sequence:

1. Initial data collection and a fatal flaw analysis, to check the grid, land availability and irradiation.
2. A memorandum of understanding, giving the parties a secure basis to continue.
3. A feasibility study covering the land, the grid and measured solar incidence.
4. Legal, technical and financial due diligence.
5. Financing and structuring.
6. Construction and operation.

This front-loads the cheap questions. If the grid cannot take 30 MW, or the land cannot be secured for the life of the project, it is better to know before significant money is spent.

Two agreements underpin the whole project. The first is a land lease or purchase of at least 20 years, with all permits and licences, including an environmental impact assessment and planning permission. The second is a power purchase agreement with a creditworthy off-taker, because the revenue stream decides whether the investment can be financed.

On environmental effects, the proposal’s view was that solar parks have a minor local impact: panel wash-water for removing airborne dust, vehicle emissions from servicing, and the land taken. The generation itself is silent and has no direct emissions. Compare this with the UK government’s planning guidance on renewable and low carbon energy, which covers land use, glare and ecology for solar farms in England.

What to consider for your own project

1. Secure the land and the grid first. Both can stop a project, and both take longer than the construction.
2. Measure the sunshine. Use site data for the feasibility study, rather than relying on regional averages.
3. Test the soil. Depth to bedrock decides whether you can use simple screw foundations.
4. Phase the build. Batches of a few megawatts let you align construction with grid capacity and finance.
5. Plan for degradation. Energy output will be lower in year 20 than in year 1.

FAQ

How much land does 1 MW of solar need?

Typically about 2 hectares, or 1.5 hectares on larger sites. The panel area itself is about 15,000 m² per MW in the layout shown.

How long does it take to install a solar PV plant?

The proposal used about four weeks per megawatt with a crew of around 20, so 5 MW batches every six months are realistic when materials and approvals are in place.

What foundations do solar racking systems use?

Where the topsoil is at least 1.6 m deep, helical steel screws can be used without concrete or pre-drilling.

Why does the grid connection distance matter?

AC cabling is expensive over long distances, so a shorter run lowers the installation cost.

Planning a solar or hybrid energy park?

Tell us about your site and grid connection and we will outline a feasibility route.