Getting ready for winter with solar

Grid Charging vs. Generator Charging for Solar Batteries

When your solar panels aren’t pulling their weight, you’ll need an alternative to keep your batteries topped up. The two main contenders are your grid connection or a generator.

Facts:

• Grid Power: Readily available for most homes in the UK.
• Generators: Provide independence from the grid, crucial during outages. For home backup and battery charging, you’re looking at generators typically in the 8kW range or higher, as they need to power your home and charge simultaneously. “Long-run” models are designed for extended operation.

Pros and Cons:

Grid Charging:

• Pros:
  • Convenience: Simple to use; just plug in.
  • Silent Operation: No noise pollution.
  • Low Maintenance: Requires very little upkeep from the homeowner.
• Cons:
  • Reliability Issues: As you mentioned, the grid can be prone to failure during peak winter demand, precisely when you need it most.
  • Ongoing Costs: You’re subject to fluctuating electricity prices and standing charges.
  • No Off-Grid Capability: If the grid goes down, so does your charging source.

Generator Charging:

• Pros:
  • Grid Independence: Provides power during outages, ensuring your home remains powered and batteries charged.
  • Long-Term Cost-Effectiveness (Potentially): While there’s an initial outlay (around £2,500 for an 8kW long-run model), the cost per kWh can, over time and depending on fuel prices, work out cheaper than grid electricity.
  • Portability: Can be used in remote locations without grid access.
• Cons:
  • Initial Investment: Higher upfront cost compared to simply using the grid.
  • Fuel Costs: Requires a constant supply of fuel (petrol, diesel, LPG, natural gas), adding to operational expenses.
  • Noise and Emissions: Generators are noisy and produce exhaust fumes, requiring proper ventilation and placement.
  • Maintenance: Requires regular servicing, oil changes, and fuel management.
  • Sizing: Undersized generators won’t be able to handle both home load and battery charging simultaneously.

Examples:

Let’s revisit your numbers for a 90-day winter needing 10kWh/day (900 kWh total):

• Grid Cost: At £0.265/kWh and factoring in standing charges, the total annual cost is approximately £475.75.
• Generator Payback: If the generator itself costs £2,500, and assuming “free fuel” for simplicity (though this isn’t truly the case, it highlights the potential saving on kWh cost), it would take roughly 5.25 years to pay off based purely on power cost savings compared to the grid. When considering fuel costs, this payback period will extend.

---

Optimising Your Winter Solar Array

Standard rooftop solar arrays are often optimised for annual average production, not necessarily peak winter performance. Here’s how to boost your solar output when the sun is low.

Facts:

• Winter Sun Angle: In the UK, the sun is significantly lower in the sky during winter, reducing the efficiency of fixed-angle rooftop panels.
• Production Boost: A purpose-built winter solar array can increase solar production by up to 50% during the colder months.

Pros and Cons:

Dedicated Winter Array/Optimisation:

• Pros:
  • Increased Winter Yield: Maximises the output from the limited winter sun, reducing reliance on other power sources.
  • Improved Efficiency: Panels can be angled optimally for the lower winter sun.
  • Enhanced Energy Independence: Reduces your energy bill and carbon footprint even in challenging conditions.
• Cons:
  • Additional Cost: Requires investment in more panels, mounting, and potentially additional charge controllers or AC devices.
  • Space Requirements: A dedicated ground-mounted array needs available land.
  • Complexity: May involve more complex wiring and system integration.

Examples:

• Charge Controller: A Maximum Power Point Tracking (MPPT) charge controller is crucial. It optimises the voltage and current from your solar panels to efficiently charge your batteries, especially important when light levels are low.
• AC Device/Second System: For existing grid-tied systems, an AC-coupled solution can convert surplus solar power to AC for battery storage or direct use. Alternatively, adding a completely separate DC-coupled system dedicated to winter charging can be highly effective.
• “Standby Array” (Parallel Array): This concept involves a second, often ground-mounted, array that can be deployed specifically when the sun’s angle is low. It can be particularly effective with a “smart solar array” or advanced charge controller that can manage inputs from multiple sources and optimise for morning and evening low-light conditions even in summer.

---

Alternative Renewable Energy Sources for Winter

While solar is great, considering other renewable sources can provide a more consistent energy supply, especially during winter.

Wind Power

Facts:

• Intermittency: Wind is highly variable; it’s often present during the day but can drop off at night. It comes in “gusts” rather than a steady stream.
• Location Criticality: Most residential locations in the UK are not ideal for capitalising on wind power due to obstructions and insufficient consistent wind speeds.
• Small Turbine Output: A typical 600W domestic wind turbine might only generate around 40W on average in many residential settings. Significant power requires large, tall turbines, which are difficult to get planning permission for.

Pros and Cons:

• Pros:
  • Complements Solar: Can generate power when solar isn’t (e.g., cloudy, windy days).
  • Reduced Carbon Footprint: Clean energy source.
• Cons:
  • Low Power Output (Small Scale): Unrealistic expectations for significant power generation from small residential turbines.
  • Noise Pollution: Can be noisy, especially larger units.
  • Visual Impact: Larger turbines can be visually intrusive.
  • Planning Permission: Larger installations almost certainly require complex planning permission.
  • Location Dependent: Only viable in very specific, exposed locations with consistent high wind speeds.

Examples:

• A 600W residential wind turbine might be considered, but unless you live on an exposed hill or coastal area, its contribution to your energy needs will likely be minimal. Forget about powering your whole home with one of these.

---

Hydro Power

Facts:

• Resource Dependent: Requires a consistent flow of water and a sufficient “head” (vertical drop) to generate power.
• High Energy Density: Water can store significant energy, making hydro a more consistent power source than wind in suitable locations.
• Average Output: A small hydro unit can average around 600W, but this can translate to significant daily energy due to continuous flow. A 600W hydro unit could produce around 14.4 kWh per day.

Pros and Cons:

• Pros:
  • Consistent Power: Unlike solar or wind, hydro can generate power 24/7 if the water flow is constant.
  • High Output: A 600W unit can produce considerably more energy per day than a similar-rated wind turbine.
  • Long Lifespan: Hydro systems are generally robust and have a long operational life.
  • Lower Maintenance (Relative to Output): While requiring initial setup and some ongoing maintenance, the energy yield can justify it.
• Cons:
  • Location Specific: Only viable if you have access to a reliable water source with a good drop.
  • High Initial Cost: Can be expensive to install due to civil engineering requirements (dams, pipes, etc.).
  • Logistical Challenges: Obtaining water rights, constructing infrastructure, and managing environmental impact can be complex.
  • Maintenance: Requires regular checks for debris, wear and tear, and flow management.

Examples:

• If you’re fortunate enough to have a stream or river on your property with a suitable gradient, a small hydro turbine could be an excellent consistent power source. At 14.4 kWh/day, this translates to about £3.81 per day in electricity savings at £0.265/kWh, making it a powerful contender for winter energy.

---

Ultimately, the best winter energy strategy for your solar system in the UK will depend on your specific circumstances, budget, and access to resources. Do any of these options sound particularly appealing or challenging for your situation?