What is a photovoltaic pier mould?
A photovoltaic pier (also called a solar pier, PV support base, concrete solar block or, on rooftop projects, a PV ballast block) is the small precast concrete block that a solar panel support structure sits on or bolts to. The mould is the plastic form these blocks are cast in. Because every block in a solar array must share identical dimensions and bolt positions, contractors precast hundreds or thousands of them in reusable plastic moulds rather than pouring in place — faster, cleaner and dimensionally consistent.
Zhihua's catalogue PV pier moulds produce two finished sizes — 30 × 20 × 30 cm and 30 × 30 × 30 cm — in a plain (flat-top) version and a grooved version with a pre-formed slot/cable recess in the top. Beyond these, solar foundation blocks are one of the most commonly customised moulds we make, because foundation geometry is set by the racking system and the site, not by a universal standard.
Where PV piers are used — three different projects, three different blocks
- Ground-mounted utility & commercial solar farms. Rows of tilted panels on fixed-tilt racking. Each post or racking foot is anchored to a concrete block (or to a driven pile — see below). Blocks need lifting points, bolt pockets that match the racking supplier's hole pattern, and a finish that can sit outdoors for 25+ years.
- Rooftop distributed solar (commercial/industrial roofs). Because you cannot drill through a waterproof roof membrane, arrays are held down by ballast blocks that rely on weight, not penetration. These blocks must be heavy enough for wind uplift but the total roof load must stay under the structure's limit — so the block size and count are an engineering calculation, not a guess.
- Single-axis trackers. Tracker rows rotate and apply cyclic, eccentric loads to their foundations. Tracker foundations are not interchangeable with fixed-tilt blocks; the mould must match the tracker vendor's foundation drawing exactly, and the concrete/steel arrangement is typically vendor-specified.
Fixed-tilt vs tracker foundations — why the mould differs
Fixed-tilt arrays use static, evenly-loaded blocks: a square or rectangular pier with bolt pockets for the racking column is usually enough, and the loads are predictable vertical and wind forces. Single-axis tracker foundations carry a moving, eccentric load and a torque arm — the block (or pile cap) is sized by the tracker manufacturer for overturning and torsion. A tracker foundation mould is therefore almost always a custom mould from the racking/tracker vendor's foundation drawing, with specific anchor positions, embed plates or anchor-bolt spread. Ordering a generic fixed-tilt block for a tracker row is one of the most common and expensive mismatches we see.
Ground blocks vs roof ballast blocks — do not treat them as the same product
On the ground, the block's job is to hold the racking down and in position; weight is rarely the limiting factor, and embed plates or cast-in anchor bolts transfer the load. On a roof, the block's entire job is weight (ballast), spread over enough area not to damage the membrane, while keeping total load inside the roof's point-load and overall-load limits. A roof ballast block is often a lower, wider, flatter shape (with a recess to cradle the rail) rather than a tall square pier. If your project is rooftop, tell us the roof allowable load (kg/m²), wind zone and the racking rail section — the block is then sized backwards from the engineering, not chosen from a catalogue.
What to get exactly right on the drawing (the parts that break projects)
- Bolt / anchor layout. The spacing, thread size (commonly M10–M16 for small blocks, larger for trackers) and projection of the anchor bolts, or the position of cast-in embed plates, must match your racking. A 10 mm bolt-position error means the post does not mount. Send the racking supplier's foundation detail, not just a photo of a block.
- Bolt pockets vs cast-in bolts. A bolt pocket (a recess you set an anchor into later) gives adjustment on site; a cast-in bolt/embed plate is faster to install but must be perfect. The mould is built differently for each.
- Cable grooves. The grooved pier has a pre-formed slot so the string cable can route under or alongside the block without a separate conduit crossing. Confirm the groove width/depth matches your cable bundle.
- Lifting / handling detail. Blocks of 50–200 kg need either a lifting insert, a hand-hole or a shape that can be grabbed. Specify how blocks are placed on site.
- Reinforcement. Larger ballast and tracker blocks may need rebar or wire mesh; the mould must suit reinforced pours and vibration.
How much concrete, and how many blocks?
A 30 × 30 × 30 cm solid block is roughly 0.027 m³ of concrete — about 60–65 kg at normal 2,300–2,400 kg/m³ reinforced density (a plain, unreinforced mix is a little lighter). The 30 × 20 × 30 cm block is about 0.018 m³, roughly 40–43 kg. Use these only as estimating figures — the real weight follows the actual mix and whether the block is solid or has a recess.
Block count depends on the racking layout (typically one support per column/pier location, spaced per the wind/snow engineering). Customers most often ask us for "how many blocks per MW" — but the answer genuinely varies: fixed-tilt ground arrays, ballasted roofs and trackers each have different support spacing, and soil/wind zones change it. We recommend you count pier locations from your racking layout drawing, add a small breakage allowance, and confirm the weight per block against the site's handling and roof-load limits.
PP vs ABS for solar pier moulds
Standard square piers in the catalogue sizes cast cleanly in PP (polypropylene), which flexes during demoulding and survives 150+ pour cycles at the lowest cost. ABS is chosen when the block has deep bolt pockets, thin fin walls around recesses, cast-in embed plates (the mould holds rigid inserts that must stay aligned), or the tracker geometry needs stiffer walls that hold tight tolerance over hundreds of casts. We recommend the material once we see the block drawing and production volume.
Lead time, MOQ and ordering
Catalogue 30×20×30 and 30×30×30 pier moulds (plain and grooved) are standard and ship quickly. Custom bolt patterns, embed-plate moulds and tracker/ballast designs are made to order from your foundation drawing, typically 15–30 days after drawing approval. Mixed-SKU orders are normal (e.g. plain and grooved piers together, or piers plus the cable-trench and drainage moulds a solar site also needs) with no strict MOQ. Send the foundation/racking detail, block dimensions, quantity, destination port and the block weight target for an FOB Ningbo/Shanghai quote.
Frequently asked questions
What standard PV pier sizes are in stock?
The two catalogue sizes are 30 × 20 × 30 cm and 30 × 30 × 30 cm, each available plain (flat-top) or grooved (with a pre-formed cable/recess slot). These cover many small and distributed solar projects; utility-scale, roof-ballast and tracker foundations are usually custom.
Can you cast bolt pockets, anchor plates or cable grooves into the block?
Yes. The mould can form bolt pockets (set anchors on site), cast-in anchor bolts or embed plates (fixed in the pour), lifting points and the top cable groove. These features must be designed into the mould up front — send the racking/foundation drawing with the bolt positions and sizes.
What is the difference between a fixed-tilt pier and a tracker pier?
Fixed-tilt piers carry static vertical/wind loads and are usually simple square blocks with bolt pockets. Tracker foundations carry rotating, eccentric and torsional loads and are defined exactly by the tracker manufacturer — they are almost always custom moulds from that vendor's foundation drawing and should not be substituted with a generic block.
How heavy is a 30×30×30 solar pier?
Roughly 60–65 kg at a 2,300–2,400 kg/m³ mix (about 0.027 m³ of concrete). The 30×20×30 block is about 40–43 kg. Actual weight depends on the mix and whether the block is solid or recessed; we quote the mould to your target finished weight.
How do I size ballast blocks for a rooftop array?
From the engineering, not from a catalogue: provide the roof allowable load (kg/m²), wind zone, panel tilt and the racking rail section. The block must be heavy enough to resist wind uplift while keeping total roof load within the structure's limit. We mould the size the calculation calls for.
PP or ABS for solar pier moulds?
Plain catalogue blocks cast well in PP (150+ pours, lowest cost). Choose ABS for deep bolt pockets, thin recess walls, cast-in embed plates that must stay aligned, or tracker geometry needing tight tolerance over many casts. We recommend material after seeing the drawing.
What is the lead time and minimum order?
Catalogue pier moulds are in stock and ship fast; custom bolt patterns, embed-plate and tracker/ballast moulds are 15–30 days after drawing approval. Mixed orders (piers plus cable-trench/drainage moulds) are welcome with no strict MOQ, FOB Ningbo/Shanghai.
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Related: solar foundations also consume rebar cover spacers — see the injection moulding for rebar spacer buying guide.