Solar Power Part I


  • 90% of the solar panels in the market today are made of polycrystalline Si. The remaining 10% are made of inorganic materials.
  • The largest demand is Germany and the largest supplier is China.


  • Solar is growing at the fastest pace than other major renewable energies. Although its capacity factor is the lowest.
  • Cost wise, the PV system has dropped below 1 USD/W. The non-modular cost such as maintenance fee, racking, wiring, inverters remain pretty much the same so the falling cost of modules are the main contributors to the falling price of solar PV.

Technical words

  • Irradiance = power per unit area (watts per sqm)
  • Spectral power density = incident power per unit area and per unit wavelength
  • The sun is a black body radiator (which is not reflective and absorbs all light). The higher the temperature of black body radiator, the higher the photon energies.
  • Solar spectrum is distributed 9% UV, 44% visible range, 47% infrared.
  • The amount of irradiation is affected by things like atmospheric mix (CO2, oxygen, water).
    • 20% of irradiation is reflected by clouds, 6% by molecules and 4% earth’s surface.
    • 19% absorbed by earth’s surface
    • Total lost = 49% of irradiation when hit on earth’s surface.
  • Solar irradiance is expressed in sun hours where earth is exposed to 1000watts per sqm. Places like Spain with more sun has around 4.2 sun hours daily.




“The Grid” Analysis of America’s Energy

Image result for the grid fraying wires book

Renewable sources are still far from overtaking energy supply fully because the grid just isn’t robust enough to deal with the fluctuations in electricity being made. Oftentimes, solar panels produce more than 100% power needed in the day, and flounders at night. The extra power made in the day cannot be put aside for use later. Thus, night time demand is usually supported by firing up of more power plants. These power plants are not efficient unless ran at full capacity.

First of all, the grid is very old. It is the same grid, for the most part, that was first built from 1950s. The grid is also unstable, susceptible to crumbling at the slightest perturbance, and get overloaded easily leading to blackouts.

Back in the days, DC grids were developed based on multiple private companies each with their own generating station and lines. The first step towards universalizing access to power was invention of AC power.

Samuel Insull, Thomas Edison’s assistant, was the one that led to the centralization of the grid. He bought over infrastructure and private companies, consolidating “load” and persuading factories to purchase cheaper off-peak power resulting in more switching to general grid from private power.

Then there was a regulation, PURPA to allow for small power plants to do cogeneration (using leftover steam to generate useful heat). This broke up the monopoly structure. And in even more recent times electricity start becoming a traded commodity. Too much electricity start travelling to far, burning and degrading the lines. Upkeep of grid lines are declining as customers do not wanna pay more. Power plants often do not keep up with maintenance, or try to evade inspections.

The biggest challenge utility faces today is the problem of peak demand. Peak times happen around 5pm. That’s unfortunately when the renewables are starting to become asleep/inactive. Thus most of US evenings are powered by fossil fuels. Utilities in the past used to have up to 30% capacity margins (ie. they can fire up to 30% more power in times of emergency), while now it’s only down around 10%. While consumption of energy surges. But the entire concept of having power plants sitting idle for half the time when there’s no demand is a huge waste. It costs the same whether the plant is idle, or going full steam, and it is even more costly when they start firing up additional plants to make up for the excess capacity needed.

Smart metering is the one tool that utilities can consider upgrading themselves to keep their businesses running. Shedding 5-10% during peak hours could eliminate powering up of dirty power plants. Utilities could also monitor and control electricity (unbeknownst to some).

The bad thing about home-based grid solar is that the normal citizens who are not using solar or who cannot afford solar systems pay higher electricity rates which are used to curtail the loss of utility customers. In 2013, Germany’s two largest utilities lost $6 billion as corporate are getting off the grid. This leads to the “utility death spiral” leaving utilities with stranded assets like those big expensive power plants but aren’t used. Their initial colossal investment in fossil fuels ended in unprecedented losses.

Electric cars could well be the most viable solution for smoothing out the instability of the grid. Much like huge batteries on wheels, they could act to balance out peak load by feeding power into the grid (when they’re docked into the 2-way charger). Besides their flexibility to go anywhere and readily provide power back to the grid, they are also in lower demand at night when peak load happens. This would tie perfectly with rooftop solar when the solar power wanes at night, and the “car batteries” are plugged in to fill in the gap. Cars are only utilized about 3% daily. So if we can make use of them effectively as storage, they can be used up to 95%.

However, the drawbacks are that electric car batteries are the main holdbacks for consumers who are concerned with their lifespan and range. Which all comes down to price and costs. Denmark has provided zero tax incentive (usually 100% of car price), and also lifelong free batteries for electric cars. Another question is the costs of infrastructure for the massive expansion of charging spots in order to make the “cars as storage” dream a reality.