Q0026
The saleable output of a solar farm is the lowest of what the plant can generate, what its equipment can deliver, what its grid connection permits and what its contract or customer will purchase. Installed MW, annual generation, exported electricity and paid-for electricity are therefore different quantities.
Solar opportunities are often described by their module capacity or theoretical energy yield. Investors are paid only for eligible metered electricity under the applicable contract, after losses, availability restrictions, curtailment and other deductions.
#### 1. Installed DC capacity
`MWdc` is the combined rated capacity of the solar modules under standard test conditions. Actual site output will normally be lower because of weather, temperature and system losses.
#### 2. AC plant capacity
`MWac` is generally associated with inverter or plant-export capability. Developers often install more DC module capacity than AC inverter capacity to improve use of the AC equipment.
#### 3. Permitted export capacity
The grid-connection agreement may limit the maximum output that can be delivered at the connection point. This limit may be lower than the installed DC capacity and could be constrained by:
#### 4. Paid or saleable energy
The commercial arrangement determines which metered electricity is purchased, credited or treated as excess. Not every exported MWh necessarily earns the main contracted price.
Annual generation depends on:
A credible model should calculate monthly and hourly output, not only multiply MW by a generic capacity factor.
Installing additional DC capacity can increase morning, evening and cloudy-period output, improving use of the AC connection. During strong sunlight, however, the modules may produce more than the inverter or export limit, causing clipping.
The optimal ratio balances:
Current CRESS clarification leaves the DC/AC ratio to the developer, subject to the wider project and connection requirements. Energy Commission CRESS technical clarification
The plant may be technically able to generate but unable to export because of:
The Energy Commission’s LSS guidelines govern how prospective plants connect to electricity networks. LSS connection guidelines
The commercial importance depends on whether curtailed energy is:
Under an LSS arrangement, the relevant power-purchase contract defines delivery, metering, performance and payment.
Under CRESS, output is linked to a green consumer through the grid. The project must distinguish:
The Energy Commission’s earlier CRESS clarification defined excess energy as output above the relevant consumer requirement and treated it differently from the principal bilateral supply. Current treatment must be verified under the latest guidelines. CRESS programme and guidelines
A project also loses saleable output through:
Performance guarantees should distinguish resource shortfall from equipment underperformance.
Storage may increase saleable output when it:
It will not help if it cannot charge during the constrained period, discharge later or receive sufficient value for the shifted energy.
For a specific project:
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