Nicaraguan Clean Energy Context

Solar powered air conditioning is a satisfying thing to experience. Imagine yourself cooling out in climate-controlled luxury, while the bright sun floods a tropical wonderland outside, and you are feeling great all the while because you get to use the power of that same sun to stay cool and dry! Complete, comfortable energy independence.

Now THAT is a lot of PV

We live in truly exciting times for alternative energy technologies and an evolution of how we think globally about energy. One of the things that always impressed me about Nicaragua, despite of (or perhaps because of) the early stage of development in this emerging economy, is the focus the policymakers in government have on energy independence and sustainable energy sources.

Don’t touch my solar cells!

2 square meter panels from Germany

As compared to only about 11% renewable source energy in the USA, Nicaragua has one of the largest current renewable source grids (just over 50%!) and has the largest global renewable source target: 74% by 2018 and 91% by 2027 according to the excellent Bloomberg climatescope reports.

And why not, the country has ‘jumped over’ the industrial revolution, and moved straight from an agrarian economy to a modern high-tech economy, and has abundant supply of all sustainable sources of clean energy – including wind, solar, hydro, geothermal and biomass.

This clean energy opportunity has brought some of the latest technologies to the country, and I was excited to visit a 15 Megawatt solar installation some of my friends recently built here in Nicaragua using German suppliers and tech.

Big Sky Ranch Off-Grid System Design

Within this context, as we began planning and developing Big Sky Ranch Nicaragua over the last two years, we realized there was an opportunity to do something interesting and design from scratch an off-grid modern home, replete with all the comforts of contemporary living (including power hungry A/C, washer dryer, <high speed internet>, swimming pool/pump) that could be delivered cost effectively.

Grid electricity in Nicaragua is still pretty expensive, and so in this market we are already at the ‘frontier moment’ when solar powered air-conditioned off-grid living has just become feasible and economically practical for the first time.

This is because the cost of solar panels and inverter technology has just dropped to affordable levels that can pay back the investment here within 5 years of normal home usage, and the efficiency of A/Cs has increased to the point where you can run them off of a reasonably sized solar system, making solar powered air conditioning the coolest newest thing.

Happily getting to apply the latest tech out here in the middle of a naturally beautiful intact ecosystem is one of the great joys for me of living in a place like Nicaragua, and so we took our original home designs inspired by Blue’s off-grid installation at Rancho Chilamate and went back to the drawing board for a a couple years to crack the interesting engineering challenge of designing a home that functions within the constraints of:

1. Comfortable and climate controlled day and night.
2. Complete energy independence – we think the modern ranch home should be off grid. Maintainable in Nicaragua.
3. Aesthetically interesting.
4. Having different options available to suit the different lifestyles of our community, the hardest technical challenge of which is solar powered air conditioning.

Passive, Green Architecture

The Big Sky Ranch Nicaragua design architect, Karin Eigner, has practical experience in designing buildings that have low energy consumption since her student days when she worked in the design and build of a passive school in South Africa and then more recently on a project here in Nicaragua with Aqua Wellness Resort.

She took this new conceptual challenge for Big Sky Ranch Nicaragua to the drawing board to architect homes that balance modern living with low energy use, a mix of climate control and natural ventilation, high ceilings and considered solar gains while remaining open to the great views at Big Sky Ranch Nicaragua, which you can read about in her posts on design.

The resulting one, two, and three bedroom designs can be seen in the homes section of the website, and were designed for any model to work on any lot.

Karin’s passive preschool design in South Africa

Options for different needs

When you break it down, the energy consumption needs of a modern ranch home in the tropics are dominated by the air conditioning requirements – both in terms of how much space needs to be cooled, for how long, and how fast. After watching how thousands of guests live in and use the spaces in our air conditioned eco-lodge Aqua Wellness resort, we decided to follow a similar model to cool the bedrooms using efficient split units, while the main living spaces make use of higher ceilings and through-ventilation instead of A/C in a balanced design. There are a number of companies that offer purpose-built solar air conditioning systems, that run all or part of their systems on low voltage, like hotspot energy, GREE international, and Solair.

Ultimately, after reviewing the design specs and discussing specialty electrical wiring requirements and maintenance/replace part requirements for these amazing new solar powered air conditioning systems that are being prototyped now, we decided that the best and most maintainable setup was still an efficient modern standard A/C unit paired with an efficient inverter and relatively standard photovoltaic solar cell (pv) setup. Karin incorporated the solar panels into a parapet roof design so that the panels are protected from the sometimes thrilling wind and still look beautiful! The geek in us did a cartwheel when Elon Musk announced his visionary solar roof tile project, but we are still waiting for the costs to come down and the technology to be proven for it to be a viable build option to offer our clients.

We feel a well balanced solar system needs a backup generator so that you don’t have to oversize the pv install and expensive battery bank for rare peak usage conditions, and to provide supplementary power when there is less solar production (if it’s cloudy). Our research led us to some very cool options for backup generation, including biogas-driven generators which are covered in this article.

Final design of solar powered air conditioning system

Ultimately we arrived at the design below that we are building into our first residential units now.

• Sun on: Roof Mounted Solar Cells -> Charge Batteries -> Inverter converts to AC voltage (110v) -> Power your regular (but efficient) home appliances.
• Sun off: Batteries -> Inverter converts to AC voltage (110v) -> Power your regular (but efficient) home appliances.
• Sun off and Batteries drained: Backup Generator -> Inverter / Charger -> Power your appliances + recharge your batteries.
• The option for a real time monitoring system via an app so the client can view their energy profile globally.

We wanted to offer three packages to our clients that fit different energy consumption and home usage needs. Our goal was to create three packages for different amounts of energy use that the solar / battery / inverter system could provide before the backup generator kicks in to supplement. Since batteries are a dominant cost item in the overall budget for a solar system, the cost-sizing of the system naturally comes down to how long you want to power your A/C after the sun goes down. We identified three usage patterns and designed systems for each usage pattern:

• Eco User: Use of A/C only during the heat of the day when the sun is shining.
• Regular User: Use of A/C until ambient temperature drops (approx sundown + 4 hours).
• Power User: Use of A/C all night if you want it.

As we went through the bidding process for vendors in Nicaragua to provide our solar powered air conditioning systems, a couple of additional opportunities presented themselves we are currently exploring, including the ability for a resident at Big Sky Ranch to sell power back from their home into an ‘off-grid grid’ that could get used by homes that are occupied from homes that are unoccupied, by the amenities (stables, hotel) when the homes have excess power – more to come on this interesting possibility.

Update [June 20, 2017]: Looks like Nicaragua is going to introduce net metering for residential pv!