Lecture Notes: Solar Cooling Technology and the Future of Energy-Efficient HVAC

One. Course Details

This is a guest lecture for EE292H Engineering and Climate Change at Stanford University, delivered by Sasha Mazzo, co-founder of New World Machines. A non-technical entrepreneur with deep experience in cleantech commercialization, Sasha shares the journey of reinventing the 170-year-old absorption chiller technology to create a low-cost, solid-state cooling system powered by solar thermal energy, waste heat, or natural gas.
The lecture covers:

• The fundamental difference between photovoltaic (PV) and solar thermal energy conversion

• The stagnation of air conditioning technology over the past 30 years

• How absorption chillers work and their historical limitations

• New World Machines’ breakthrough microchannel solid-state chiller design

• Modular system architecture and its performance advantages

• Real-world applications from commercial buildings to off-grid refrigeration

• Cleantech startup strategies for market entry and customer adoption

• An open Q&A addressing technical performance, manufacturing costs, and business models

Two. Key Learning Takeaways

• Solar thermal panels convert 60% of incoming sunlight to usable heat, compared to just 15-20% for state-of-the-art photovoltaic panels, making them far more efficient for cooling applications.

• Conventional vapor-compression air conditioning has improved by only 30% in 30 years (1% per year), lagging far behind other energy technologies like lighting and batteries.

• Absorption chillers, invented in 1850, use heat instead of electricity to produce cooling but have been limited by high cost, low reliability, and bulky mechanical design.

• New World Machines’ solid-state chiller eliminates all moving parts inside the machine, cutting manufacturing costs by 70% and reducing maintenance to near zero.

• A modular "ice book" architecture allows systems to scale from 5 tons to 500+ tons by stacking identical units, enabling dynamic load matching and fault tolerance.

• The technology achieves a COP (Coefficient of Performance) of 1.6 for single-effect operation, 75% more efficient than traditional absorption chillers.

• The most viable market entry strategy for new HVAC technologies is supplemental peak shaving rather than full system replacement, reducing customer risk and enabling 1-2 year payback periods.

Three. Course Gold Quotes

1. "Air conditioning has improved by 1% per year for 30 years. We’ve gone to the moon, invented the internet, and electrified transportation—but we still cool buildings the same way we did in 1950."

2. "The biggest mistake engineers make is building the technology first and then looking for customers. Steve Blank was right: you have to get out of the building and talk to people before you write a single line of code or cut a single sheet of metal."

3. "Solar thermal is the forgotten renewable. Everyone talks about PV, but 60% efficiency beats 20% efficiency every single time—especially when you need heat to make cold."

4. "HVAC customers are the most risk-averse people on the planet. They don’t care if your technology is revolutionary. They care if their building stays at 72 degrees 24/7."

5. "We didn’t try to make the big old absorption chiller smaller. We started from scratch and asked: what’s the smallest possible machine that can do the same job?"

6. "Waste heat is the world’s most underutilized energy resource. A third of all energy we produce is dumped as heat—we just need a way to turn it into something useful."

7. "Cleantech doesn’t win because it’s green. It wins because it saves people money. If you can’t show a clear financial return, no one will buy your product—no matter how good it is for the planet."

Four. Layered Learning Notes

Module 1: Solar Cooling Fundamentals

• Solar cooling systems use solar thermal panels to heat water, which then powers an absorption chiller to produce cold water for air conditioning.

• Key advantage: perfect load coincidence—cooling demand peaks exactly when sunlight is most abundant, eliminating the need for expensive energy storage.

• Solar thermal panel types:

  • Pool heaters: Simple rubber/plastic membranes for low-temperature applications (80-100°F)

  • Flat plate collectors: Metal plates with fluid channels, 40-50% efficient, low cost

  • Evacuated tube collectors: Tubes in a vacuum, 50-60% efficient, better in cold weather but more fragile

  • Concentrated collectors: Parabolic troughs/linear Fresnel for high-temperature applications (200+°F)

• Traditional solar cooling systems have failed commercially because they required expensive high-temperature collectors and inefficient chillers. New World Machines’ chiller operates efficiently at 160-170°F, compatible with low-cost flat plate and evacuated tube collectors.

Module 2: The Problem with Conventional HVAC

• Buildings consume 40% of U.S. energy, with 35-40% of that going to heating, ventilation, and air conditioning (HVAC).

• 80% of commercial buildings use rooftop units (RTUs), which are the least efficient, shortest-lived, and most unreliable HVAC systems available.

• Chillers are oversized for peak design conditions (e.g., 95°F days that occur 1-2 times per year), so they operate at 60-70% load 98% of the time, wasting massive amounts of energy.

• Vapor-compression chillers rely on electricity, which is only 30% efficient at the power plant (70% of energy lost in generation and transmission). Using natural gas directly in an absorption chiller is 2-3x more efficient end-to-end.

Module 3: Absorption Chiller Technology

• How absorption chillers work:

  1. A refrigerant (water) evaporates at low pressure, absorbing heat and producing cooling

  2. An absorbent (lithium bromide or ammonia) absorbs the refrigerant vapor

  3. Heat is applied to separate the refrigerant from the absorbent

  4. The refrigerant is condensed and returned to the evaporator to repeat the cycle

• Traditional absorption chillers are large, heavy machines with multiple pumps, valves, and vessels. They require frequent maintenance and are 3x more expensive than vapor-compression chillers.

• They are currently used only in industrial applications with abundant high-grade waste heat, where the energy savings justify the high capital cost.

Module 4: New World Machines’ Breakthrough Design

• The core innovation is a microchannel heat exchanger architecture that integrates the entire cooling cycle onto thin plastic sheets:

  • Channels are laser-cut or etched into 3mm thick plastic sheets

  • Sheets are sealed between steel plates to contain the working fluid

  • Multiple sheets are stacked like pages in a book ("ice book" design) to increase capacity

• All moving parts (pumps, valves) are eliminated from the internal cooling cycle, resulting in a completely solid-state machine.

• Modular design benefits:

  • Dynamic load matching: Only activate the number of units needed for current demand, eliminating part-load inefficiency

  • Fault tolerance: If one unit fails, the rest continue operating—no system downtime

  • Scalability: Build systems of any size by adding more units, no custom engineering required

  • Fast startup: Individual units can be brought online in minutes, compared to hours for traditional absorption chillers

Module 5: Applications and Use Cases

• Commercial building peak shaving: Install a 50-ton supplemental chiller to handle peak cooling loads, reducing electricity consumption during expensive tier 3/4 rate periods. Payback: 1-2 years.

• Spot cooling for data centers: Target high-heat server rooms instead of overcooling entire buildings, cutting HVAC energy use by 30-40%.

• Combined Heat and Power (CHP) integration: Use waste heat from on-site generators to produce cooling, creating a trigeneration system (electricity + heat + cooling) with 80-90% overall efficiency.

• Off-grid refrigeration: Solar-powered chillers for remote villages, hospitals, and agricultural cold storage, eliminating the need for diesel generators.

• Military applications: Forward operating bases where transporting jet fuel for generators costs $400+ per gallon.

• Transportation: Cargo ships and cruise ships with abundant waste heat from engines.

Module 6: Market Entry and Commercialization Strategy

• The biggest barrier to new HVAC technology adoption is customer risk aversion. Building managers will not replace a working system with an unproven technology.

• New World Machines’ go-to-market strategy:

  1. Position as a supplemental "pony chiller" rather than a replacement system

  2. Target customers with high electricity rates and significant peak demand charges

  3. Offer performance guarantees and cooling-as-a-service (CaaS) models to eliminate upfront cost risk

  4. Start with niche applications where the value proposition is strongest (e.g., off-grid refrigeration)

• Critical success factors:

  • Independent third-party performance verification (currently underway at Oak Ridge National Laboratory)

  • Manufacturing scale to drive costs down to parity with vapor-compression chillers

  • Leveraging existing HVAC distribution and installation channels

  • Wishing you all the creativity and persistence to reimagine the technologies we take for granted. The world needs better ways to cool our buildings, power our lives, and protect our planet—and the solutions are often hiding in plain sight, waiting for someone to look at an old problem from a new angle. Keep questioning the status quo, talking to your customers, and building technologies that don’t just work better, but make financial sense too.